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	$191.78	4.671%	$200.738	$200.74	$200.75	$200.70
Purchase #2	$135.28	3.749%	$140.3516	$140.35	$140.35	$140.40
Purchase #3	$152.53	13.259%	$172.754	$172.75	$172.75	$172.80
Purchase #4	$8.49	6.704%	$9.0592	$9.06	$9.05	$9.10
Purchase #5	$140.78	11.200%	$156.5474	$156.55	$156.55	$156.50
Purchase #6	$119.31	9.444%	$130.5776	$130.58	$130.60	$130.60
Purchase #7	$184.31	13.658%	$209.4831	$209.48	$209.50	$209.50
7 purchase totals =	$932.48		$1,019.5109	$1,019.51	$1,019.55	$1,019.60