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	$51.63	3.449%	$53.4107	$53.41	$53.40	$53.40
Purchase #2	$189.98	5.125%	$199.7165	$199.72	$199.70	$199.70
Purchase #3	$6.35	12.841%	$7.1654	$7.17	$7.15	$7.20
Purchase #4	$151.73	6.789%	$162.0309	$162.03	$162.05	$162.00
Purchase #5	$174.53	11.256%	$194.1751	$194.18	$194.20	$194.20
Purchase #6	$80.76	11.626%	$90.1492	$90.15	$90.15	$90.10
Purchase #7	$46.30	3.354%	$47.8529	$47.85	$47.85	$47.90
7 purchase totals =	$701.28		$754.5007	$754.51	$754.50	$754.50