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	$126.41	7.799%	$136.2687	$136.27	$136.25	$136.30
Purchase #2	$60.50	8.124%	$65.415	$65.42	$65.40	$65.40
Purchase #3	$212.79	3.532%	$220.3057	$220.31	$220.30	$220.30
Purchase #4	$158.33	4.572%	$165.5688	$165.57	$165.55	$165.60
Purchase #5	$43.25	5.541%	$45.6465	$45.65	$45.65	$45.60
Purchase #6	$166.53	5.222%	$175.2262	$175.23	$175.25	$175.20
Purchase #7	$51.35	11.729%	$57.3728	$57.37	$57.35	$57.40
7 purchase totals =	$819.16		$865.8037	$865.82	$865.75	$865.80