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	$70.50	3.468%	$72.9449	$72.94	$72.95	$72.90
Purchase #2	$150.69	11.508%	$168.0314	$168.03	$168.05	$168.00
Purchase #3	$121.76	13.672%	$138.407	$138.41	$138.40	$138.40
Purchase #4	$73.73	12.428%	$82.8932	$82.89	$82.90	$82.90
Purchase #5	$243.90	9.158%	$266.2364	$266.24	$266.25	$266.20
Purchase #6	$193.62	12.834%	$218.4692	$218.47	$218.45	$218.50
Purchase #7	$220.76	5.282%	$232.4205	$232.42	$232.40	$232.40
7 purchase totals =	$1,074.96		$1,179.4026	$1,179.40	$1,179.40	$1,179.30