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	$145.70	6.722%	$155.494	$155.49	$155.50	$155.50
Purchase #2	$188.54	4.148%	$196.3606	$196.36	$196.35	$196.40
Purchase #3	$52.29	5.524%	$55.1785	$55.18	$55.20	$55.20
Purchase #4	$44.78	10.766%	$49.601	$49.60	$49.60	$49.60
Purchase #5	$148.30	11.373%	$165.1662	$165.17	$165.15	$165.20
Purchase #6	$155.38	3.155%	$160.2822	$160.28	$160.30	$160.30
Purchase #7	$174.66	10.729%	$193.3993	$193.40	$193.40	$193.40
7 purchase totals =	$909.65		$975.4818	$975.48	$975.50	$975.60