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	$63.56	5.854%	$67.2808	$67.28	$67.30	$67.30
Purchase #2	$59.64	3.814%	$61.9147	$61.91	$61.90	$61.90
Purchase #3	$152.91	3.490%	$158.2466	$158.25	$158.25	$158.20
Purchase #4	$203.50	11.595%	$227.0958	$227.10	$227.10	$227.10
Purchase #5	$152.50	3.387%	$157.6652	$157.67	$157.65	$157.70
Purchase #6	$233.31	7.799%	$251.5058	$251.51	$251.50	$251.50
Purchase #7	$126.70	12.581%	$142.6401	$142.64	$142.65	$142.60
7 purchase totals =	$992.12		$1,066.3490	$1,066.36	$1,066.35	$1,066.30