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	$115.51	11.631%	$128.945	$128.95	$128.95	$128.90
Purchase #2	$179.46	6.732%	$191.5412	$191.54	$191.55	$191.50
Purchase #3	$234.57	9.711%	$257.3491	$257.35	$257.35	$257.30
Purchase #4	$55.53	6.782%	$59.296	$59.30	$59.30	$59.30
Purchase #5	$17.84	3.538%	$18.4712	$18.47	$18.45	$18.50
Purchase #6	$177.88	3.723%	$184.5025	$184.50	$184.50	$184.50
Purchase #7	$93.30	13.175%	$105.5923	$105.59	$105.60	$105.60
7 purchase totals =	$874.09		$945.6973	$945.70	$945.70	$945.60