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	$190.44	11.561%	$212.4568	$212.46	$212.45	$212.50
Purchase #2	$48.99	8.740%	$53.2717	$53.27	$53.25	$53.30
Purchase #3	$180.52	11.300%	$200.9188	$200.92	$200.90	$200.90
Purchase #4	$128.98	9.647%	$141.4227	$141.42	$141.40	$141.40
Purchase #5	$196.90	3.512%	$203.8151	$203.82	$203.80	$203.80
Purchase #6	$223.84	8.258%	$242.3247	$242.32	$242.30	$242.30
Purchase #7	$64.64	12.594%	$72.7808	$72.78	$72.80	$72.80
7 purchase totals =	$1,034.31		$1,126.9906	$1,126.99	$1,126.90	$1,127.00