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	$198.39	11.650%	$221.5024	$221.50	$221.50	$221.50
Purchase #2	$45.71	7.428%	$49.1053	$49.11	$49.10	$49.10
Purchase #3	$182.88	7.390%	$196.3948	$196.39	$196.40	$196.40
Purchase #4	$41.88	12.218%	$46.9969	$47.00	$47.00	$47.00
Purchase #5	$43.55	3.693%	$45.1583	$45.16	$45.15	$45.20
Purchase #6	$80.91	10.694%	$89.5625	$89.56	$89.55	$89.60
Purchase #7	$236.67	9.215%	$258.4791	$258.48	$258.50	$258.50
7 purchase totals =	$829.99		$907.1993	$907.20	$907.20	$907.30