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	$149.32	3.446%	$154.4656	$154.47	$154.45	$154.50
Purchase #2	$218.29	8.502%	$236.849	$236.85	$236.85	$236.80
Purchase #3	$20.61	6.647%	$21.9799	$21.98	$22.00	$22.00
Purchase #4	$79.74	13.377%	$90.4068	$90.41	$90.40	$90.40
Purchase #5	$218.63	9.749%	$239.9442	$239.94	$239.95	$239.90
Purchase #6	$227.63	12.308%	$255.6467	$255.65	$255.65	$255.60
Purchase #7	$53.90	9.528%	$59.0356	$59.04	$59.05	$59.00
7 purchase totals =	$968.12		$1,058.3278	$1,058.34	$1,058.35	$1,058.20