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	$135.96	13.366%	$154.1324	$154.13	$154.15	$154.10
Purchase #2	$33.91	11.554%	$37.828	$37.83	$37.85	$37.80
Purchase #3	$187.72	6.781%	$200.4493	$200.45	$200.45	$200.40
Purchase #4	$90.63	10.707%	$100.3338	$100.33	$100.35	$100.30
Purchase #5	$165.33	4.854%	$173.3551	$173.36	$173.35	$173.40
Purchase #6	$102.74	7.690%	$110.6407	$110.64	$110.65	$110.60
Purchase #7	$79.51	13.304%	$90.088	$90.09	$90.10	$90.10
7 purchase totals =	$795.80		$866.8273	$866.83	$866.90	$866.70