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	$201.71	3.540%	$208.8505	$208.85	$208.85	$208.90
Purchase #2	$54.34	13.864%	$61.8737	$61.87	$61.85	$61.90
Purchase #3	$34.88	10.399%	$38.5072	$38.51	$38.50	$38.50
Purchase #4	$152.74	9.712%	$167.5741	$167.57	$167.55	$167.60
Purchase #5	$46.60	9.141%	$50.8597	$50.86	$50.85	$50.90
Purchase #6	$94.87	5.309%	$99.9066	$99.91	$99.90	$99.90
Purchase #7	$24.52	9.397%	$26.8241	$26.82	$26.80	$26.80
7 purchase totals =	$609.66		$654.3959	$654.39	$654.30	$654.50