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	$42.56	4.109%	$44.3088	$44.31	$44.30	$44.30
Purchase #2	$58.85	5.781%	$62.2521	$62.25	$62.25	$62.30
Purchase #3	$50.87	5.749%	$53.7945	$53.79	$53.80	$53.80
Purchase #4	$55.97	6.452%	$59.5812	$59.58	$59.60	$59.60
Purchase #5	$212.48	11.827%	$237.61	$237.61	$237.60	$237.60
Purchase #6	$51.58	7.776%	$55.5909	$55.59	$55.60	$55.60
Purchase #7	$128.33	8.153%	$138.7927	$138.79	$138.80	$138.80
7 purchase totals =	$600.64		$651.9302	$651.92	$651.95	$652.00