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	$210.81	3.132%	$217.4126	$217.41	$217.40	$217.40
Purchase #2	$156.59	3.343%	$161.8248	$161.82	$161.80	$161.80
Purchase #3	$28.44	7.155%	$30.4749	$30.47	$30.45	$30.50
Purchase #4	$137.56	13.568%	$156.2241	$156.22	$156.20	$156.20
Purchase #5	$213.61	4.227%	$222.6393	$222.64	$222.65	$222.60
Purchase #6	$156.53	3.850%	$162.5564	$162.56	$162.55	$162.60
Purchase #7	$132.27	13.312%	$149.8778	$149.88	$149.90	$149.90
7 purchase totals =	$1,035.81		$1,101.0099	$1,101.00	$1,100.95	$1,101.00