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	$147.39	10.222%	$162.4562	$162.46	$162.45	$162.50
Purchase #2	$53.32	12.411%	$59.9375	$59.94	$59.95	$59.90
Purchase #3	$225.73	3.281%	$233.1362	$233.14	$233.15	$233.10
Purchase #4	$76.55	12.525%	$86.1379	$86.14	$86.15	$86.10
Purchase #5	$48.71	8.498%	$52.8494	$52.85	$52.85	$52.80
Purchase #6	$83.57	7.154%	$89.5486	$89.55	$89.55	$89.50
Purchase #7	$38.67	4.504%	$40.4117	$40.41	$40.40	$40.40
7 purchase totals =	$673.94		$724.4775	$724.49	$724.50	$724.30