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	$124.27	6.223%	$132.0033	$132.00	$132.00	$132.00
Purchase #2	$39.76	11.340%	$44.2688	$44.27	$44.25	$44.30
Purchase #3	$120.71	4.244%	$125.8329	$125.83	$125.85	$125.80
Purchase #4	$186.58	10.190%	$205.5925	$205.59	$205.60	$205.60
Purchase #5	$56.29	11.118%	$62.5483	$62.55	$62.55	$62.50
Purchase #6	$235.45	4.179%	$245.2895	$245.29	$245.30	$245.30
Purchase #7	$88.61	11.611%	$98.8985	$98.90	$98.90	$98.90
7 purchase totals =	$851.67		$914.4338	$914.43	$914.45	$914.40