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	$92.93	4.400%	$97.0189	$97.02	$97.00	$97.00
Purchase #2	$77.46	11.158%	$86.103	$86.10	$86.10	$86.10
Purchase #3	$199.67	4.345%	$208.3457	$208.35	$208.35	$208.30
Purchase #4	$59.31	13.865%	$67.5333	$67.53	$67.55	$67.50
Purchase #5	$160.47	7.575%	$172.6256	$172.63	$172.65	$172.60
Purchase #6	$48.45	10.336%	$53.4578	$53.46	$53.45	$53.50
Purchase #7	$130.91	9.447%	$143.2771	$143.28	$143.30	$143.30
7 purchase totals =	$769.20		$828.3614	$828.37	$828.40	$828.30