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	$79.96	6.808%	$85.4037	$85.40	$85.40	$85.40
Purchase #2	$102.45	11.568%	$114.3014	$114.30	$114.30	$114.30
Purchase #3	$159.40	11.460%	$177.6672	$177.67	$177.65	$177.70
Purchase #4	$146.27	13.393%	$165.8599	$165.86	$165.85	$165.90
Purchase #5	$55.27	4.731%	$57.8848	$57.88	$57.90	$57.90
Purchase #6	$235.92	8.718%	$256.4875	$256.49	$256.50	$256.50
Purchase #7	$202.70	3.171%	$209.1276	$209.13	$209.15	$209.10
7 purchase totals =	$981.97		$1,066.7321	$1,066.73	$1,066.75	$1,066.80