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	$151.62	12.860%	$171.1183	$171.12	$171.10	$171.10
Purchase #2	$168.59	13.405%	$191.1895	$191.19	$191.20	$191.20
Purchase #3	$57.44	13.637%	$65.2731	$65.27	$65.25	$65.30
Purchase #4	$188.83	9.290%	$206.3723	$206.37	$206.35	$206.40
Purchase #5	$124.43	12.866%	$140.4392	$140.44	$140.45	$140.40
Purchase #6	$113.87	8.424%	$123.4624	$123.46	$123.45	$123.50
Purchase #7	$113.54	11.754%	$126.8855	$126.89	$126.90	$126.90
7 purchase totals =	$918.32		$1,024.7403	$1,024.74	$1,024.70	$1,024.80