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	$187.71	6.742%	$200.3654	$200.37	$200.35	$200.40
Purchase #2	$144.35	8.161%	$156.1304	$156.13	$156.15	$156.10
Purchase #3	$172.55	9.283%	$188.5678	$188.57	$188.55	$188.60
Purchase #4	$236.48	7.518%	$254.2586	$254.26	$254.25	$254.30
Purchase #5	$37.80	13.449%	$42.8837	$42.88	$42.90	$42.90
Purchase #6	$149.53	11.197%	$166.2729	$166.27	$166.25	$166.30
Purchase #7	$237.65	10.146%	$261.762	$261.76	$261.75	$261.80
7 purchase totals =	$1,166.07		$1,270.2408	$1,270.24	$1,270.20	$1,270.40