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	$45.62	8.288%	$49.401	$49.40	$49.40	$49.40
Purchase #2	$243.84	7.608%	$262.3913	$262.39	$262.40	$262.40
Purchase #3	$94.90	5.832%	$100.4346	$100.43	$100.45	$100.40
Purchase #4	$206.32	4.714%	$216.0459	$216.05	$216.05	$216.00
Purchase #5	$142.47	9.784%	$156.4093	$156.41	$156.40	$156.40
Purchase #6	$123.78	13.136%	$140.0397	$140.04	$140.05	$140.00
Purchase #7	$206.52	11.292%	$229.8402	$229.84	$229.85	$229.80
7 purchase totals =	$1,063.45		$1,154.5620	$1,154.56	$1,154.60	$1,154.40