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	$141.45	7.692%	$152.3303	$152.33	$152.35	$152.30
Purchase #2	$54.64	11.229%	$60.7755	$60.78	$60.80	$60.80
Purchase #3	$248.29	7.484%	$266.872	$266.87	$266.85	$266.90
Purchase #4	$39.77	4.143%	$41.4177	$41.42	$41.40	$41.40
Purchase #5	$185.58	5.314%	$195.4417	$195.44	$195.45	$195.40
Purchase #6	$142.54	12.839%	$160.8407	$160.84	$160.85	$160.80
Purchase #7	$61.35	7.116%	$65.7157	$65.72	$65.70	$65.70
7 purchase totals =	$873.62		$943.3936	$943.40	$943.40	$943.30