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	$189.38	11.625%	$211.3954	$211.40	$211.40	$211.40
Purchase #2	$229.44	6.235%	$243.7456	$243.75	$243.75	$243.70
Purchase #3	$63.52	13.238%	$71.9288	$71.93	$71.95	$71.90
Purchase #4	$147.77	9.455%	$161.7417	$161.74	$161.75	$161.70
Purchase #5	$232.93	7.142%	$249.5659	$249.57	$249.55	$249.60
Purchase #6	$37.71	12.331%	$42.36	$42.36	$42.35	$42.40
Purchase #7	$77.75	3.684%	$80.6143	$80.61	$80.60	$80.60
7 purchase totals =	$978.50		$1,061.3517	$1,061.36	$1,061.35	$1,061.30