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	$203.27	11.256%	$226.1501	$226.15	$226.15	$226.20
Purchase #2	$74.48	9.387%	$81.4714	$81.47	$81.45	$81.50
Purchase #3	$104.37	6.637%	$111.297	$111.30	$111.30	$111.30
Purchase #4	$126.98	9.513%	$139.0596	$139.06	$139.05	$139.10
Purchase #5	$79.54	7.578%	$85.5675	$85.57	$85.55	$85.60
Purchase #6	$98.67	10.870%	$109.3954	$109.40	$109.40	$109.40
Purchase #7	$20.31	5.578%	$21.4429	$21.44	$21.45	$21.40
7 purchase totals =	$707.62		$774.3839	$774.39	$774.35	$774.50