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	$105.81	13.697%	$120.3028	$120.30	$120.30	$120.30
Purchase #2	$6.58	4.733%	$6.8914	$6.89	$6.90	$6.90
Purchase #3	$144.85	3.609%	$150.0776	$150.08	$150.10	$150.10
Purchase #4	$169.79	5.476%	$179.0877	$179.09	$179.10	$179.10
Purchase #5	$202.82	12.594%	$228.3632	$228.36	$228.35	$228.40
Purchase #6	$155.89	4.168%	$162.3875	$162.39	$162.40	$162.40
Purchase #7	$223.77	3.618%	$231.866	$231.87	$231.85	$231.90
7 purchase totals =	$1,009.51		$1,078.9762	$1,078.98	$1,079.00	$1,079.10