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	$176.92	7.381%	$189.9785	$189.98	$190.00	$190.00
Purchase #2	$209.49	9.520%	$229.4334	$229.43	$229.45	$229.40
Purchase #3	$32.69	13.666%	$37.1574	$37.16	$37.15	$37.20
Purchase #4	$92.79	5.119%	$97.5399	$97.54	$97.55	$97.50
Purchase #5	$138.60	11.366%	$154.3533	$154.35	$154.35	$154.40
Purchase #6	$164.35	6.728%	$175.4075	$175.41	$175.40	$175.40
Purchase #7	$131.27	4.381%	$137.0209	$137.02	$137.00	$137.00
7 purchase totals =	$946.11		$1,020.8909	$1,020.89	$1,020.90	$1,020.90