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	$177.39	4.814%	$185.9296	$185.93	$185.95	$185.90
Purchase #2	$142.61	7.271%	$152.9792	$152.98	$153.00	$153.00
Purchase #3	$186.28	10.830%	$206.4541	$206.45	$206.45	$206.50
Purchase #4	$163.59	4.203%	$170.4657	$170.47	$170.45	$170.50
Purchase #5	$172.94	7.297%	$185.5594	$185.56	$185.55	$185.60
Purchase #6	$135.48	4.604%	$141.7175	$141.72	$141.70	$141.70
Purchase #7	$59.84	3.284%	$61.8051	$61.81	$61.80	$61.80
7 purchase totals =	$1,038.13		$1,104.9106	$1,104.92	$1,104.90	$1,105.00