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	$174.66	7.731%	$188.163	$188.16	$188.15	$188.20
Purchase #2	$80.25	12.450%	$90.2411	$90.24	$90.25	$90.20
Purchase #3	$33.64	6.617%	$35.866	$35.87	$35.85	$35.90
Purchase #4	$201.37	9.809%	$221.1224	$221.12	$221.10	$221.10
Purchase #5	$52.33	3.600%	$54.2139	$54.21	$54.20	$54.20
Purchase #6	$16.60	11.858%	$18.5684	$18.57	$18.55	$18.60
Purchase #7	$92.94	12.309%	$104.38	$104.38	$104.40	$104.40
7 purchase totals =	$651.79		$712.5548	$712.55	$712.50	$712.60