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	$130.39	13.603%	$148.127	$148.13	$148.15	$148.10
Purchase #2	$218.63	9.849%	$240.1629	$240.16	$240.15	$240.20
Purchase #3	$149.75	13.258%	$169.6039	$169.60	$169.60	$169.60
Purchase #4	$29.81	9.609%	$32.6744	$32.67	$32.65	$32.70
Purchase #5	$52.51	11.304%	$58.4457	$58.45	$58.45	$58.40
Purchase #6	$184.44	13.443%	$209.2343	$209.23	$209.25	$209.20
Purchase #7	$36.36	13.654%	$41.3246	$41.32	$41.30	$41.30
7 purchase totals =	$801.89		$899.5728	$899.56	$899.55	$899.50