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	$231.67	10.177%	$255.2471	$255.25	$255.25	$255.20
Purchase #2	$67.55	6.266%	$71.7827	$71.78	$71.80	$71.80
Purchase #3	$221.94	8.661%	$241.1622	$241.16	$241.15	$241.20
Purchase #4	$16.54	9.744%	$18.1517	$18.15	$18.15	$18.20
Purchase #5	$93.35	8.377%	$101.1699	$101.17	$101.15	$101.20
Purchase #6	$241.41	6.350%	$256.7395	$256.74	$256.75	$256.70
Purchase #7	$59.93	9.363%	$65.5412	$65.54	$65.55	$65.50
7 purchase totals =	$932.39		$1,009.7943	$1,009.79	$1,009.80	$1,009.80