Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$127.41	11.135%	$141.5971	$141.60	$141.60	$141.60
Purchase #2	$203.72	3.316%	$210.4754	$210.48	$210.50	$210.50
Purchase #3	$118.79	11.606%	$132.5768	$132.58	$132.60	$132.60
Purchase #4	$135.74	11.631%	$151.5279	$151.53	$151.55	$151.50
Purchase #5	$101.39	10.129%	$111.6598	$111.66	$111.65	$111.70
Purchase #6	$225.33	3.299%	$232.7636	$232.76	$232.75	$232.80
Purchase #7	$97.89	4.704%	$102.4947	$102.49	$102.50	$102.50
7 purchase totals =	$1,010.27		$1,083.0953	$1,083.10	$1,083.15	$1,083.20