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	$168.43	7.411%	$180.9123	$180.91	$180.90	$180.90
Purchase #2	$245.83	8.328%	$266.3027	$266.30	$266.30	$266.30
Purchase #3	$32.59	5.729%	$34.4571	$34.46	$34.45	$34.50
Purchase #4	$42.69	6.398%	$45.4213	$45.42	$45.40	$45.40
Purchase #5	$86.93	5.217%	$91.4651	$91.47	$91.45	$91.50
Purchase #6	$29.40	11.640%	$32.8222	$32.82	$32.80	$32.80
Purchase #7	$48.37	4.710%	$50.6482	$50.65	$50.65	$50.60
7 purchase totals =	$654.24		$702.0289	$702.03	$701.95	$702.00