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	$166.47	7.818%	$179.4846	$179.48	$179.50	$179.50
Purchase #2	$156.86	13.754%	$178.4345	$178.43	$178.45	$178.40
Purchase #3	$50.95	6.270%	$54.1446	$54.14	$54.15	$54.10
Purchase #4	$49.61	6.484%	$52.8267	$52.83	$52.85	$52.80
Purchase #5	$197.69	12.607%	$222.6128	$222.61	$222.60	$222.60
Purchase #6	$140.92	5.631%	$148.8552	$148.86	$148.85	$148.90
Purchase #7	$158.83	4.158%	$165.4342	$165.43	$165.45	$165.40
7 purchase totals =	$921.33		$1,001.7926	$1,001.78	$1,001.85	$1,001.70