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	$164.74	7.164%	$176.542	$176.54	$176.55	$176.50
Purchase #2	$39.86	13.326%	$45.1717	$45.17	$45.15	$45.20
Purchase #3	$80.71	7.450%	$86.7229	$86.72	$86.70	$86.70
Purchase #4	$130.41	12.604%	$146.8469	$146.85	$146.85	$146.80
Purchase #5	$14.62	6.237%	$15.5318	$15.53	$15.55	$15.50
Purchase #6	$136.36	6.668%	$145.4525	$145.45	$145.45	$145.50
Purchase #7	$128.59	6.201%	$136.5639	$136.56	$136.55	$136.60
7 purchase totals =	$695.29		$752.8317	$752.82	$752.80	$752.80