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	$210.56	8.562%	$228.5881	$228.59	$228.60	$228.60
Purchase #2	$241.82	13.485%	$274.4294	$274.43	$274.45	$274.40
Purchase #3	$85.88	10.421%	$94.8296	$94.83	$94.85	$94.80
Purchase #4	$205.69	13.822%	$234.1205	$234.12	$234.10	$234.10
Purchase #5	$242.27	10.505%	$267.7205	$267.72	$267.70	$267.70
Purchase #6	$179.76	9.276%	$196.4345	$196.43	$196.45	$196.40
Purchase #7	$75.36	7.371%	$80.9148	$80.91	$80.90	$80.90
7 purchase totals =	$1,241.34		$1,377.0374	$1,377.03	$1,377.05	$1,376.90