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	$95.83	9.835%	$105.2549	$105.25	$105.25	$105.30
Purchase #2	$95.75	4.730%	$100.279	$100.28	$100.30	$100.30
Purchase #3	$93.93	7.127%	$100.6244	$100.62	$100.60	$100.60
Purchase #4	$230.74	9.133%	$251.8135	$251.81	$251.80	$251.80
Purchase #5	$83.60	5.428%	$88.1378	$88.14	$88.15	$88.10
Purchase #6	$220.29	6.834%	$235.3446	$235.34	$235.35	$235.30
Purchase #7	$76.54	7.708%	$82.4397	$82.44	$82.45	$82.40
7 purchase totals =	$896.68		$963.8939	$963.88	$963.90	$963.80