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	$162.96	10.143%	$179.489	$179.49	$179.50	$179.50
Purchase #2	$39.47	7.841%	$42.5648	$42.56	$42.55	$42.60
Purchase #3	$170.32	10.371%	$187.9839	$187.98	$188.00	$188.00
Purchase #4	$100.97	4.512%	$105.5258	$105.53	$105.55	$105.50
Purchase #5	$92.34	3.383%	$95.4639	$95.46	$95.45	$95.50
Purchase #6	$44.27	3.249%	$45.7083	$45.71	$45.70	$45.70
Purchase #7	$205.27	3.200%	$211.8386	$211.84	$211.85	$211.80
7 purchase totals =	$815.60		$868.5743	$868.57	$868.60	$868.60