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	$165.73	12.478%	$186.4098	$186.41	$186.40	$186.40
Purchase #2	$63.35	12.619%	$71.3441	$71.34	$71.35	$71.30
Purchase #3	$25.70	4.419%	$26.8357	$26.84	$26.85	$26.80
Purchase #4	$156.29	10.388%	$172.5254	$172.53	$172.55	$172.50
Purchase #5	$194.72	6.870%	$208.0973	$208.10	$208.10	$208.10
Purchase #6	$38.82	12.136%	$43.5312	$43.53	$43.55	$43.50
Purchase #7	$170.79	6.838%	$182.4686	$182.47	$182.45	$182.50
7 purchase totals =	$815.40		$891.2121	$891.22	$891.25	$891.10