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	$91.75	12.610%	$103.3197	$103.32	$103.30	$103.30
Purchase #2	$117.39	8.393%	$127.2425	$127.24	$127.25	$127.20
Purchase #3	$20.89	6.280%	$22.2019	$22.20	$22.20	$22.20
Purchase #4	$223.69	7.670%	$240.847	$240.85	$240.85	$240.80
Purchase #5	$37.37	5.130%	$39.2871	$39.29	$39.30	$39.30
Purchase #6	$150.35	12.194%	$168.6837	$168.68	$168.70	$168.70
Purchase #7	$74.68	10.514%	$82.5319	$82.53	$82.55	$82.50
7 purchase totals =	$716.12		$784.1138	$784.11	$784.15	$784.00