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	$102.31	3.700%	$106.0955	$106.10	$106.10	$106.10
Purchase #2	$50.87	5.743%	$53.7915	$53.79	$53.80	$53.80
Purchase #3	$183.27	4.122%	$190.8244	$190.82	$190.80	$190.80
Purchase #4	$161.74	4.695%	$169.3337	$169.33	$169.35	$169.30
Purchase #5	$243.89	10.506%	$269.5131	$269.51	$269.50	$269.50
Purchase #6	$150.74	5.173%	$158.5378	$158.54	$158.55	$158.50
Purchase #7	$154.55	7.516%	$166.166	$166.17	$166.15	$166.20
7 purchase totals =	$1,047.37		$1,114.2620	$1,114.26	$1,114.25	$1,114.20