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	$79.73	3.389%	$82.432	$82.43	$82.45	$82.40
Purchase #2	$194.62	8.841%	$211.8264	$211.83	$211.85	$211.80
Purchase #3	$222.98	10.237%	$245.8065	$245.81	$245.80	$245.80
Purchase #4	$34.98	13.511%	$39.7061	$39.71	$39.70	$39.70
Purchase #5	$77.54	9.853%	$85.18	$85.18	$85.20	$85.20
Purchase #6	$159.73	3.729%	$165.6863	$165.69	$165.70	$165.70
Purchase #7	$221.73	8.793%	$241.2267	$241.23	$241.25	$241.20
7 purchase totals =	$991.31		$1,071.8640	$1,071.88	$1,071.95	$1,071.80