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	$165.61	3.824%	$171.9429	$171.94	$171.95	$171.90
Purchase #2	$187.68	3.680%	$194.5866	$194.59	$194.60	$194.60
Purchase #3	$172.73	5.313%	$181.9071	$181.91	$181.90	$181.90
Purchase #4	$215.31	3.483%	$222.8092	$222.81	$222.80	$222.80
Purchase #5	$83.50	10.468%	$92.2408	$92.24	$92.25	$92.20
Purchase #6	$62.67	12.626%	$70.5827	$70.58	$70.60	$70.60
Purchase #7	$191.65	9.432%	$209.7264	$209.73	$209.75	$209.70
7 purchase totals =	$1,079.15		$1,143.7957	$1,143.80	$1,143.85	$1,143.70