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	$42.51	10.326%	$46.8996	$46.90	$46.90	$46.90
Purchase #2	$160.88	4.601%	$168.2821	$168.28	$168.30	$168.30
Purchase #3	$94.41	11.304%	$105.0821	$105.08	$105.10	$105.10
Purchase #4	$10.28	12.861%	$11.6021	$11.60	$11.60	$11.60
Purchase #5	$147.46	11.557%	$164.502	$164.50	$164.50	$164.50
Purchase #6	$148.91	3.831%	$154.6147	$154.61	$154.60	$154.60
Purchase #7	$215.68	3.826%	$223.9319	$223.93	$223.95	$223.90
7 purchase totals =	$820.13		$874.9145	$874.90	$874.95	$874.90