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	$196.74	4.821%	$206.2248	$206.22	$206.20	$206.20
Purchase #2	$178.98	12.143%	$200.7135	$200.71	$200.70	$200.70
Purchase #3	$152.95	12.740%	$172.4358	$172.44	$172.45	$172.40
Purchase #4	$75.90	5.765%	$80.2756	$80.28	$80.30	$80.30
Purchase #5	$99.63	12.312%	$111.8964	$111.90	$111.90	$111.90
Purchase #6	$126.46	7.119%	$135.4627	$135.46	$135.45	$135.50
Purchase #7	$23.85	5.502%	$25.1622	$25.16	$25.15	$25.20
7 purchase totals =	$854.51		$932.1710	$932.17	$932.15	$932.20