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	$212.98	12.118%	$238.7889	$238.79	$238.80	$238.80
Purchase #2	$176.64	8.383%	$191.4477	$191.45	$191.45	$191.40
Purchase #3	$162.31	12.450%	$182.5176	$182.52	$182.50	$182.50
Purchase #4	$156.61	10.157%	$172.5169	$172.52	$172.50	$172.50
Purchase #5	$52.65	4.176%	$54.8487	$54.85	$54.85	$54.80
Purchase #6	$123.55	3.332%	$127.6667	$127.67	$127.65	$127.70
Purchase #7	$185.93	11.183%	$206.7226	$206.72	$206.70	$206.70
7 purchase totals =	$1,070.67		$1,174.5091	$1,174.52	$1,174.45	$1,174.40