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	$215.44	4.585%	$225.3179	$225.32	$225.30	$225.30
Purchase #2	$131.69	7.263%	$141.2546	$141.25	$141.25	$141.30
Purchase #3	$68.89	3.738%	$71.4651	$71.47	$71.45	$71.50
Purchase #4	$78.89	13.732%	$89.7232	$89.72	$89.70	$89.70
Purchase #5	$128.57	3.346%	$132.872	$132.87	$132.85	$132.90
Purchase #6	$158.46	10.507%	$175.1094	$175.11	$175.10	$175.10
Purchase #7	$155.60	7.203%	$166.8079	$166.81	$166.80	$166.80
7 purchase totals =	$937.54		$1,002.5501	$1,002.55	$1,002.45	$1,002.60