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	$47.98	11.690%	$53.5889	$53.59	$53.60	$53.60
Purchase #2	$61.26	6.479%	$65.229	$65.23	$65.25	$65.20
Purchase #3	$120.39	13.482%	$136.621	$136.62	$136.60	$136.60
Purchase #4	$88.39	12.606%	$99.5324	$99.53	$99.55	$99.50
Purchase #5	$33.70	10.143%	$37.1182	$37.12	$37.10	$37.10
Purchase #6	$190.45	5.410%	$200.7533	$200.75	$200.75	$200.80
Purchase #7	$216.76	7.398%	$232.7959	$232.80	$232.80	$232.80
7 purchase totals =	$758.93		$825.6387	$825.64	$825.65	$825.60