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	$78.90	8.605%	$85.6893	$85.69	$85.70	$85.70
Purchase #2	$183.60	9.434%	$200.9208	$200.92	$200.90	$200.90
Purchase #3	$182.46	4.768%	$191.1597	$191.16	$191.15	$191.20
Purchase #4	$93.35	8.807%	$101.5713	$101.57	$101.55	$101.60
Purchase #5	$127.62	10.430%	$140.9308	$140.93	$140.95	$140.90
Purchase #6	$182.40	6.438%	$194.1429	$194.14	$194.15	$194.10
Purchase #7	$176.37	7.317%	$189.275	$189.28	$189.30	$189.30
7 purchase totals =	$1,024.70		$1,103.6898	$1,103.69	$1,103.70	$1,103.70