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	$49.61	9.348%	$54.2475	$54.25	$54.25	$54.20
Purchase #2	$29.69	13.263%	$33.6278	$33.63	$33.65	$33.60
Purchase #3	$91.89	8.573%	$99.7677	$99.77	$99.75	$99.80
Purchase #4	$162.72	6.847%	$173.8614	$173.86	$173.85	$173.90
Purchase #5	$201.77	4.214%	$210.2726	$210.27	$210.25	$210.30
Purchase #6	$130.80	8.782%	$142.2869	$142.29	$142.30	$142.30
Purchase #7	$241.42	11.632%	$269.502	$269.50	$269.50	$269.50
7 purchase totals =	$907.90		$983.5659	$983.57	$983.55	$983.60