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	$211.75	5.390%	$223.1633	$223.16	$223.15	$223.20
Purchase #2	$57.59	3.553%	$59.6362	$59.64	$59.65	$59.60
Purchase #3	$195.82	6.550%	$208.6462	$208.65	$208.65	$208.60
Purchase #4	$90.39	6.848%	$96.5799	$96.58	$96.60	$96.60
Purchase #5	$34.78	5.131%	$36.5646	$36.56	$36.55	$36.60
Purchase #6	$142.65	12.185%	$160.0319	$160.03	$160.05	$160.00
Purchase #7	$104.86	13.803%	$119.3338	$119.33	$119.35	$119.30
7 purchase totals =	$837.84		$903.9559	$903.95	$904.00	$903.90