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	$165.37	4.685%	$173.1176	$173.12	$173.10	$173.10
Purchase #2	$140.71	4.837%	$147.5161	$147.52	$147.50	$147.50
Purchase #3	$39.38	10.514%	$43.5204	$43.52	$43.50	$43.50
Purchase #4	$23.72	3.472%	$24.5436	$24.54	$24.55	$24.50
Purchase #5	$111.84	3.504%	$115.7589	$115.76	$115.75	$115.80
Purchase #6	$37.46	6.602%	$39.9331	$39.93	$39.95	$39.90
Purchase #7	$182.34	3.196%	$188.1676	$188.17	$188.15	$188.20
7 purchase totals =	$700.82		$732.5573	$732.56	$732.50	$732.50