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	$127.50	9.116%	$139.1229	$139.12	$139.10	$139.10
Purchase #2	$199.79	11.493%	$222.7519	$222.75	$222.75	$222.80
Purchase #3	$118.53	9.192%	$129.4253	$129.43	$129.45	$129.40
Purchase #4	$240.35	5.752%	$254.1749	$254.17	$254.15	$254.20
Purchase #5	$152.49	9.211%	$166.5359	$166.54	$166.55	$166.50
Purchase #6	$65.65	8.387%	$71.1561	$71.16	$71.15	$71.20
Purchase #7	$115.49	11.816%	$129.1363	$129.14	$129.15	$129.10
7 purchase totals =	$1,019.80		$1,112.3033	$1,112.31	$1,112.30	$1,112.30