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	$164.61	8.366%	$178.3813	$178.38	$178.40	$178.40
Purchase #2	$119.61	11.311%	$133.1391	$133.14	$133.15	$133.10
Purchase #3	$250.49	4.842%	$262.6187	$262.62	$262.60	$262.60
Purchase #4	$37.39	12.344%	$42.0054	$42.01	$42.00	$42.00
Purchase #5	$110.72	12.191%	$124.2179	$124.22	$124.20	$124.20
Purchase #6	$95.32	10.401%	$105.2342	$105.23	$105.25	$105.20
Purchase #7	$209.31	3.123%	$215.8468	$215.85	$215.85	$215.80
7 purchase totals =	$987.45		$1,061.4434	$1,061.45	$1,061.45	$1,061.30