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	$160.82	8.439%	$174.3916	$174.39	$174.40	$174.40
Purchase #2	$152.72	7.764%	$164.5772	$164.58	$164.60	$164.60
Purchase #3	$80.43	7.779%	$86.6866	$86.69	$86.70	$86.70
Purchase #4	$197.48	5.634%	$208.606	$208.61	$208.60	$208.60
Purchase #5	$246.59	7.430%	$264.9116	$264.91	$264.90	$264.90
Purchase #6	$98.89	10.346%	$109.1212	$109.12	$109.10	$109.10
Purchase #7	$30.78	10.221%	$33.926	$33.93	$33.95	$33.90
7 purchase totals =	$967.71		$1,042.2202	$1,042.23	$1,042.25	$1,042.20