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	$85.31	7.738%	$91.9113	$91.91	$91.90	$91.90
Purchase #2	$178.90	3.720%	$185.5551	$185.56	$185.55	$185.60
Purchase #3	$91.59	7.669%	$98.614	$98.61	$98.60	$98.60
Purchase #4	$20.47	4.428%	$21.3764	$21.38	$21.40	$21.40
Purchase #5	$48.38	4.105%	$50.366	$50.37	$50.35	$50.40
Purchase #6	$20.41	13.378%	$23.1404	$23.14	$23.15	$23.10
Purchase #7	$222.73	12.704%	$251.0256	$251.03	$251.05	$251.00
7 purchase totals =	$667.79		$721.9888	$722.00	$722.00	$722.00