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	$113.78	9.731%	$124.8519	$124.85	$124.85	$124.90
Purchase #2	$192.80	10.643%	$213.3197	$213.32	$213.30	$213.30
Purchase #3	$38.82	12.234%	$43.5692	$43.57	$43.55	$43.60
Purchase #4	$123.83	11.177%	$137.6705	$137.67	$137.65	$137.70
Purchase #5	$191.56	13.272%	$216.9838	$216.98	$217.00	$217.00
Purchase #6	$149.82	4.638%	$156.7687	$156.77	$156.75	$156.80
Purchase #7	$124.41	12.576%	$140.0558	$140.06	$140.05	$140.10
7 purchase totals =	$935.02		$1,033.2196	$1,033.22	$1,033.15	$1,033.40