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	$118.38	6.342%	$125.8877	$125.89	$125.90	$125.90
Purchase #2	$26.62	5.700%	$28.1373	$28.14	$28.15	$28.10
Purchase #3	$222.59	6.719%	$237.5458	$237.55	$237.55	$237.50
Purchase #4	$107.28	10.739%	$118.8008	$118.80	$118.80	$118.80
Purchase #5	$100.77	10.686%	$111.5383	$111.54	$111.55	$111.50
Purchase #6	$210.62	4.313%	$219.704	$219.70	$219.70	$219.70
Purchase #7	$68.57	4.414%	$71.5967	$71.60	$71.60	$71.60
7 purchase totals =	$854.83		$913.2106	$913.22	$913.25	$913.10