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	$107.32	3.768%	$111.3638	$111.36	$111.35	$111.40
Purchase #2	$176.70	10.843%	$195.8596	$195.86	$195.85	$195.90
Purchase #3	$79.30	13.467%	$89.9793	$89.98	$90.00	$90.00
Purchase #4	$186.98	13.679%	$212.557	$212.56	$212.55	$212.60
Purchase #5	$165.86	11.112%	$184.2904	$184.29	$184.30	$184.30
Purchase #6	$47.91	7.108%	$51.3154	$51.32	$51.30	$51.30
Purchase #7	$111.74	4.119%	$116.3426	$116.34	$116.35	$116.30
7 purchase totals =	$875.81		$961.7081	$961.71	$961.70	$961.80