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	$156.58	12.645%	$176.3795	$176.38	$176.40	$176.40
Purchase #2	$76.87	7.742%	$82.8213	$82.82	$82.80	$82.80
Purchase #3	$31.97	4.621%	$33.4473	$33.45	$33.45	$33.40
Purchase #4	$168.84	7.133%	$180.8834	$180.88	$180.90	$180.90
Purchase #5	$155.53	4.522%	$162.5631	$162.56	$162.55	$162.60
Purchase #6	$109.61	4.436%	$114.4723	$114.47	$114.45	$114.50
Purchase #7	$169.81	8.658%	$184.5121	$184.51	$184.50	$184.50
7 purchase totals =	$869.21		$935.0790	$935.07	$935.05	$935.10