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	$163.30	4.864%	$171.2429	$171.24	$171.25	$171.20
Purchase #2	$248.42	11.434%	$276.8243	$276.82	$276.80	$276.80
Purchase #3	$37.98	8.285%	$41.1266	$41.13	$41.15	$41.10
Purchase #4	$90.35	5.143%	$94.9967	$95.00	$95.00	$95.00
Purchase #5	$85.66	5.244%	$90.152	$90.15	$90.15	$90.20
Purchase #6	$173.72	3.247%	$179.3607	$179.36	$179.35	$179.40
Purchase #7	$211.31	13.845%	$240.5659	$240.57	$240.55	$240.60
7 purchase totals =	$1,010.74		$1,094.2691	$1,094.27	$1,094.25	$1,094.30