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	$56.96	4.744%	$59.6622	$59.66	$59.65	$59.70
Purchase #2	$137.71	10.615%	$152.3279	$152.33	$152.35	$152.30
Purchase #3	$96.93	6.756%	$103.4786	$103.48	$103.50	$103.50
Purchase #4	$173.55	10.594%	$191.9359	$191.94	$191.95	$191.90
Purchase #5	$20.70	9.819%	$22.7325	$22.73	$22.75	$22.70
Purchase #6	$169.85	3.830%	$176.3553	$176.36	$176.35	$176.40
Purchase #7	$230.90	12.513%	$259.7925	$259.79	$259.80	$259.80
7 purchase totals =	$886.60		$966.2849	$966.29	$966.35	$966.30