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	$131.39	4.611%	$137.4484	$137.45	$137.45	$137.40
Purchase #2	$169.84	7.669%	$182.865	$182.87	$182.85	$182.90
Purchase #3	$89.45	4.570%	$93.5379	$93.54	$93.55	$93.50
Purchase #4	$21.76	12.708%	$24.5253	$24.53	$24.55	$24.50
Purchase #5	$242.75	5.202%	$255.3779	$255.38	$255.40	$255.40
Purchase #6	$157.47	11.376%	$175.3838	$175.38	$175.40	$175.40
Purchase #7	$211.29	5.805%	$223.5554	$223.56	$223.55	$223.60
7 purchase totals =	$1,023.95		$1,092.6937	$1,092.71	$1,092.75	$1,092.70