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	$188.82	12.632%	$212.6717	$212.67	$212.65	$212.70
Purchase #2	$147.27	13.512%	$167.1691	$167.17	$167.15	$167.20
Purchase #3	$143.93	3.423%	$148.8567	$148.86	$148.85	$148.90
Purchase #4	$127.67	4.874%	$133.8926	$133.89	$133.90	$133.90
Purchase #5	$123.33	11.781%	$137.8595	$137.86	$137.85	$137.90
Purchase #6	$46.36	12.851%	$52.3177	$52.32	$52.30	$52.30
Purchase #7	$234.93	4.413%	$245.2975	$245.30	$245.30	$245.30
7 purchase totals =	$1,012.31		$1,098.0648	$1,098.07	$1,098.00	$1,098.20