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	$154.40	8.245%	$167.1303	$167.13	$167.15	$167.10
Purchase #2	$180.35	6.130%	$191.4055	$191.41	$191.40	$191.40
Purchase #3	$188.46	11.371%	$209.8898	$209.89	$209.90	$209.90
Purchase #4	$62.28	8.373%	$67.4947	$67.49	$67.50	$67.50
Purchase #5	$195.57	10.617%	$216.3337	$216.33	$216.35	$216.30
Purchase #6	$150.48	5.763%	$159.1522	$159.15	$159.15	$159.20
Purchase #7	$34.92	13.675%	$39.6953	$39.70	$39.70	$39.70
7 purchase totals =	$966.46		$1,051.1015	$1,051.10	$1,051.15	$1,051.10