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	$213.72	9.119%	$233.2091	$233.21	$233.20	$233.20
Purchase #2	$81.55	9.557%	$89.3437	$89.34	$89.35	$89.30
Purchase #3	$211.32	5.495%	$222.932	$222.93	$222.95	$222.90
Purchase #4	$59.38	3.741%	$61.6014	$61.60	$61.60	$61.60
Purchase #5	$142.63	9.399%	$156.0358	$156.04	$156.05	$156.00
Purchase #6	$223.31	10.108%	$245.8822	$245.88	$245.90	$245.90
Purchase #7	$195.99	13.432%	$222.3154	$222.32	$222.30	$222.30
7 purchase totals =	$1,127.90		$1,231.3196	$1,231.32	$1,231.35	$1,231.20