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	$93.32	13.740%	$106.1422	$106.14	$106.15	$106.10
Purchase #2	$44.92	3.362%	$46.4302	$46.43	$46.45	$46.40
Purchase #3	$62.79	5.853%	$66.4651	$66.47	$66.45	$66.50
Purchase #4	$95.39	10.564%	$105.467	$105.47	$105.45	$105.50
Purchase #5	$164.91	13.593%	$187.3262	$187.33	$187.35	$187.30
Purchase #6	$87.89	9.704%	$96.4188	$96.42	$96.40	$96.40
Purchase #7	$84.45	4.398%	$88.1641	$88.16	$88.15	$88.20
7 purchase totals =	$633.67		$696.4136	$696.42	$696.40	$696.40