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	$113.77	8.591%	$123.544	$123.54	$123.55	$123.50
Purchase #2	$249.33	6.628%	$265.8556	$265.86	$265.85	$265.90
Purchase #3	$99.33	10.493%	$109.7527	$109.75	$109.75	$109.80
Purchase #4	$58.30	4.260%	$60.7836	$60.78	$60.80	$60.80
Purchase #5	$47.78	10.690%	$52.8877	$52.89	$52.90	$52.90
Purchase #6	$184.88	4.741%	$193.6452	$193.65	$193.65	$193.60
Purchase #7	$51.65	7.726%	$55.6405	$55.64	$55.65	$55.60
7 purchase totals =	$805.04		$862.1093	$862.11	$862.15	$862.10