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	$44.94	11.586%	$50.1467	$50.15	$50.15	$50.10
Purchase #2	$183.96	13.647%	$209.065	$209.07	$209.05	$209.10
Purchase #3	$100.95	8.847%	$109.881	$109.88	$109.90	$109.90
Purchase #4	$54.71	8.817%	$59.5338	$59.53	$59.55	$59.50
Purchase #5	$84.62	8.741%	$92.0166	$92.02	$92.00	$92.00
Purchase #6	$232.41	4.268%	$242.3293	$242.33	$242.35	$242.30
Purchase #7	$173.87	9.749%	$190.8206	$190.82	$190.80	$190.80
7 purchase totals =	$875.46		$953.7930	$953.80	$953.80	$953.70