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	$172.98	5.627%	$182.7136	$182.71	$182.70	$182.70
Purchase #2	$6.67	6.347%	$7.0933	$7.09	$7.10	$7.10
Purchase #3	$42.59	7.638%	$45.843	$45.84	$45.85	$45.80
Purchase #4	$140.82	5.481%	$148.5383	$148.54	$148.55	$148.50
Purchase #5	$216.37	3.495%	$223.9321	$223.93	$223.95	$223.90
Purchase #6	$196.99	11.356%	$219.3602	$219.36	$219.35	$219.40
Purchase #7	$81.31	11.240%	$90.4492	$90.45	$90.45	$90.40
7 purchase totals =	$857.73		$917.9297	$917.92	$917.95	$917.80