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	$112.46	7.175%	$120.529	$120.53	$120.55	$120.50
Purchase #2	$92.54	7.531%	$99.5092	$99.51	$99.50	$99.50
Purchase #3	$49.33	6.284%	$52.4299	$52.43	$52.45	$52.40
Purchase #4	$23.52	8.236%	$25.4571	$25.46	$25.45	$25.50
Purchase #5	$77.97	13.266%	$88.3135	$88.31	$88.30	$88.30
Purchase #6	$28.41	13.232%	$32.1692	$32.17	$32.15	$32.20
Purchase #7	$91.79	6.628%	$97.8738	$97.87	$97.85	$97.90
7 purchase totals =	$476.02		$516.2817	$516.28	$516.25	$516.30