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	$147.32	6.351%	$156.6763	$156.68	$156.70	$156.70
Purchase #2	$33.63	11.865%	$37.6202	$37.62	$37.60	$37.60
Purchase #3	$63.29	7.332%	$67.9304	$67.93	$67.95	$67.90
Purchase #4	$59.52	9.731%	$65.3119	$65.31	$65.30	$65.30
Purchase #5	$129.63	13.612%	$147.2752	$147.28	$147.30	$147.30
Purchase #6	$217.92	11.474%	$242.9241	$242.92	$242.90	$242.90
Purchase #7	$37.28	12.369%	$41.8912	$41.89	$41.90	$41.90
7 purchase totals =	$688.59		$759.6293	$759.63	$759.65	$759.60