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	$160.41	3.179%	$165.5094	$165.51	$165.50	$165.50
Purchase #2	$227.91	13.308%	$258.2403	$258.24	$258.25	$258.20
Purchase #3	$250.74	4.263%	$261.429	$261.43	$261.45	$261.40
Purchase #4	$170.30	10.740%	$188.5902	$188.59	$188.60	$188.60
Purchase #5	$75.28	5.712%	$79.58	$79.58	$79.60	$79.60
Purchase #6	$75.93	8.345%	$82.2664	$82.27	$82.25	$82.30
Purchase #7	$243.32	6.688%	$259.5932	$259.59	$259.60	$259.60
7 purchase totals =	$1,203.89		$1,295.2085	$1,295.21	$1,295.25	$1,295.20