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	$130.89	7.639%	$140.8887	$140.89	$140.90	$140.90
Purchase #2	$108.47	13.411%	$123.0169	$123.02	$123.00	$123.00
Purchase #3	$148.25	4.854%	$155.4461	$155.45	$155.45	$155.40
Purchase #4	$162.37	11.709%	$181.3819	$181.38	$181.40	$181.40
Purchase #5	$30.55	9.396%	$33.4205	$33.42	$33.40	$33.40
Purchase #6	$53.90	9.252%	$58.8868	$58.89	$58.90	$58.90
Purchase #7	$56.29	3.521%	$58.272	$58.27	$58.25	$58.30
7 purchase totals =	$690.72		$751.3129	$751.32	$751.30	$751.30