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	$149.48	10.732%	$165.5222	$165.52	$165.50	$165.50
Purchase #2	$238.27	11.590%	$265.8855	$265.89	$265.90	$265.90
Purchase #3	$191.30	10.416%	$211.2258	$211.23	$211.25	$211.20
Purchase #4	$194.81	7.564%	$209.5454	$209.55	$209.55	$209.50
Purchase #5	$71.50	10.757%	$79.1913	$79.19	$79.20	$79.20
Purchase #6	$98.57	6.736%	$105.2097	$105.21	$105.20	$105.20
Purchase #7	$90.28	6.205%	$95.8819	$95.88	$95.90	$95.90
7 purchase totals =	$1,034.21		$1,132.4618	$1,132.47	$1,132.50	$1,132.40