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	$182.39	7.856%	$196.7186	$196.72	$196.70	$196.70
Purchase #2	$82.27	10.461%	$90.8763	$90.88	$90.90	$90.90
Purchase #3	$84.29	11.513%	$93.9943	$93.99	$94.00	$94.00
Purchase #4	$244.84	13.518%	$277.9375	$277.94	$277.95	$277.90
Purchase #5	$130.61	9.305%	$142.7633	$142.76	$142.75	$142.80
Purchase #6	$198.93	5.644%	$210.1576	$210.16	$210.15	$210.20
Purchase #7	$99.26	3.695%	$102.9277	$102.93	$102.95	$102.90
7 purchase totals =	$1,022.59		$1,115.3753	$1,115.38	$1,115.40	$1,115.40