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	$145.93	10.465%	$161.2016	$161.20	$161.20	$161.20
Purchase #2	$117.72	11.671%	$131.4591	$131.46	$131.45	$131.50
Purchase #3	$162.27	7.301%	$174.1173	$174.12	$174.10	$174.10
Purchase #4	$41.66	11.761%	$46.5596	$46.56	$46.55	$46.60
Purchase #5	$77.66	11.631%	$86.6926	$86.69	$86.70	$86.70
Purchase #6	$60.95	9.808%	$66.928	$66.93	$66.95	$66.90
Purchase #7	$37.42	7.190%	$40.1105	$40.11	$40.10	$40.10
7 purchase totals =	$643.61		$707.0687	$707.07	$707.05	$707.10