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	$203.95	3.340%	$210.7619	$210.76	$210.75	$210.80
Purchase #2	$67.78	5.450%	$71.474	$71.47	$71.45	$71.50
Purchase #3	$116.30	6.223%	$123.5373	$123.54	$123.55	$123.50
Purchase #4	$130.60	11.424%	$145.5197	$145.52	$145.50	$145.50
Purchase #5	$150.28	12.833%	$169.5654	$169.57	$169.55	$169.60
Purchase #6	$153.85	8.835%	$167.4426	$167.44	$167.45	$167.40
Purchase #7	$218.37	11.462%	$243.3996	$243.40	$243.40	$243.40
7 purchase totals =	$1,041.13		$1,131.7005	$1,131.70	$1,131.65	$1,131.70