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	$54.25	6.844%	$57.9629	$57.96	$57.95	$58.00
Purchase #2	$194.89	4.319%	$203.3073	$203.31	$203.30	$203.30
Purchase #3	$82.81	3.734%	$85.9021	$85.90	$85.90	$85.90
Purchase #4	$143.72	3.378%	$148.5749	$148.57	$148.55	$148.60
Purchase #5	$66.67	4.631%	$69.7575	$69.76	$69.75	$69.80
Purchase #6	$56.80	4.738%	$59.4912	$59.49	$59.50	$59.50
Purchase #7	$183.33	9.443%	$200.6419	$200.64	$200.65	$200.60
7 purchase totals =	$782.47		$825.6378	$825.63	$825.60	$825.70