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	$64.79	12.663%	$72.9944	$72.99	$73.00	$73.00
Purchase #2	$55.51	7.164%	$59.4867	$59.49	$59.50	$59.50
Purchase #3	$57.91	5.807%	$61.2728	$61.27	$61.25	$61.30
Purchase #4	$208.75	12.663%	$235.184	$235.18	$235.20	$235.20
Purchase #5	$128.77	9.280%	$140.7199	$140.72	$140.70	$140.70
Purchase #6	$147.71	13.155%	$167.1413	$167.14	$167.15	$167.10
Purchase #7	$111.87	7.786%	$120.5802	$120.58	$120.60	$120.60
7 purchase totals =	$775.31		$857.3793	$857.37	$857.40	$857.40