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	$79.33	3.858%	$82.3906	$82.39	$82.40	$82.40
Purchase #2	$217.79	11.339%	$242.4852	$242.49	$242.50	$242.50
Purchase #3	$88.72	4.619%	$92.818	$92.82	$92.80	$92.80
Purchase #4	$109.91	12.442%	$123.585	$123.59	$123.60	$123.60
Purchase #5	$98.36	4.364%	$102.6524	$102.65	$102.65	$102.70
Purchase #6	$248.82	9.177%	$271.6542	$271.65	$271.65	$271.70
Purchase #7	$103.52	7.673%	$111.4631	$111.46	$111.45	$111.50
7 purchase totals =	$946.45		$1,027.0485	$1,027.05	$1,027.05	$1,027.20