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	$85.71	5.852%	$90.7257	$90.73	$90.75	$90.70
Purchase #2	$244.38	9.423%	$267.4079	$267.41	$267.40	$267.40
Purchase #3	$119.29	11.570%	$133.0919	$133.09	$133.10	$133.10
Purchase #4	$88.71	11.871%	$99.2408	$99.24	$99.25	$99.20
Purchase #5	$52.29	4.419%	$54.6007	$54.60	$54.60	$54.60
Purchase #6	$33.59	9.852%	$36.8993	$36.90	$36.90	$36.90
Purchase #7	$214.26	13.617%	$243.4358	$243.44	$243.45	$243.40
7 purchase totals =	$838.23		$925.4021	$925.41	$925.45	$925.30