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	$13.26	6.530%	$14.1259	$14.13	$14.15	$14.10
Purchase #2	$37.84	5.789%	$40.0306	$40.03	$40.05	$40.00
Purchase #3	$63.56	6.494%	$67.6876	$67.69	$67.70	$67.70
Purchase #4	$128.88	8.758%	$140.1673	$140.17	$140.15	$140.20
Purchase #5	$159.42	9.237%	$174.1456	$174.15	$174.15	$174.10
Purchase #6	$68.71	5.511%	$72.4966	$72.50	$72.50	$72.50
Purchase #7	$56.53	8.444%	$61.3034	$61.30	$61.30	$61.30
7 purchase totals =	$528.20		$569.9570	$569.97	$570.00	$569.90