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	$202.94	8.470%	$220.129	$220.13	$220.15	$220.10
Purchase #2	$148.33	12.640%	$167.0789	$167.08	$167.10	$167.10
Purchase #3	$104.82	6.432%	$111.562	$111.56	$111.55	$111.60
Purchase #4	$185.35	6.845%	$198.0372	$198.04	$198.05	$198.00
Purchase #5	$54.37	8.733%	$59.1181	$59.12	$59.10	$59.10
Purchase #6	$36.55	13.743%	$41.5731	$41.57	$41.55	$41.60
Purchase #7	$67.33	4.693%	$70.4898	$70.49	$70.50	$70.50
7 purchase totals =	$799.69		$867.9881	$867.99	$868.00	$868.00