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	$98.31	5.681%	$103.895	$103.90	$103.90	$103.90
Purchase #2	$48.70	9.182%	$53.1716	$53.17	$53.15	$53.20
Purchase #3	$76.85	13.378%	$87.131	$87.13	$87.15	$87.10
Purchase #4	$241.65	3.827%	$250.8979	$250.90	$250.90	$250.90
Purchase #5	$37.93	9.292%	$41.4545	$41.45	$41.45	$41.50
Purchase #6	$98.56	6.543%	$105.0088	$105.01	$105.00	$105.00
Purchase #7	$135.86	11.731%	$151.7977	$151.80	$151.80	$151.80
7 purchase totals =	$737.86		$793.3565	$793.36	$793.35	$793.40