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	$66.43	12.483%	$74.7225	$74.72	$74.70	$74.70
Purchase #2	$52.60	13.812%	$59.8651	$59.87	$59.85	$59.90
Purchase #3	$91.30	7.498%	$98.1457	$98.15	$98.15	$98.10
Purchase #4	$50.44	13.503%	$57.2509	$57.25	$57.25	$57.30
Purchase #5	$161.61	11.635%	$180.4133	$180.41	$180.40	$180.40
Purchase #6	$22.77	3.320%	$23.526	$23.53	$23.55	$23.50
Purchase #7	$249.32	3.683%	$258.5025	$258.50	$258.50	$258.50
7 purchase totals =	$694.47		$752.4260	$752.43	$752.40	$752.40