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	$153.30	3.146%	$158.1228	$158.12	$158.10	$158.10
Purchase #2	$45.69	7.685%	$49.2013	$49.20	$49.20	$49.20
Purchase #3	$81.61	6.217%	$86.6837	$86.68	$86.70	$86.70
Purchase #4	$90.61	10.855%	$100.4457	$100.45	$100.45	$100.40
Purchase #5	$88.99	10.547%	$98.3758	$98.38	$98.40	$98.40
Purchase #6	$55.44	11.589%	$61.8649	$61.86	$61.85	$61.90
Purchase #7	$88.32	12.692%	$99.5296	$99.53	$99.55	$99.50
7 purchase totals =	$603.96		$654.2238	$654.22	$654.25	$654.20