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	$116.25	6.847%	$124.2096	$124.21	$124.20	$124.20
Purchase #2	$145.39	11.530%	$162.1535	$162.15	$162.15	$162.20
Purchase #3	$154.26	5.601%	$162.9001	$162.90	$162.90	$162.90
Purchase #4	$250.27	6.221%	$265.8393	$265.84	$265.85	$265.80
Purchase #5	$89.80	6.475%	$95.6146	$95.61	$95.60	$95.60
Purchase #6	$167.25	3.185%	$172.5769	$172.58	$172.60	$172.60
Purchase #7	$90.63	12.260%	$101.7412	$101.74	$101.75	$101.70
7 purchase totals =	$1,013.85		$1,085.0352	$1,085.03	$1,085.05	$1,085.00