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	$229.47	10.650%	$253.9086	$253.91	$253.90	$253.90
Purchase #2	$108.61	9.706%	$119.1517	$119.15	$119.15	$119.20
Purchase #3	$63.73	5.500%	$67.2352	$67.24	$67.25	$67.20
Purchase #4	$220.78	6.704%	$235.5811	$235.58	$235.60	$235.60
Purchase #5	$17.71	13.703%	$20.1368	$20.14	$20.15	$20.10
Purchase #6	$142.33	7.373%	$152.824	$152.82	$152.80	$152.80
Purchase #7	$159.57	5.829%	$168.8713	$168.87	$168.85	$168.90
7 purchase totals =	$942.20		$1,017.7087	$1,017.71	$1,017.70	$1,017.70