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	$111.91	10.508%	$123.6695	$123.67	$123.65	$123.70
Purchase #2	$85.56	11.546%	$95.4388	$95.44	$95.45	$95.40
Purchase #3	$168.72	11.718%	$188.4906	$188.49	$188.50	$188.50
Purchase #4	$200.32	13.258%	$226.8784	$226.88	$226.90	$226.90
Purchase #5	$129.65	13.826%	$147.5754	$147.58	$147.60	$147.60
Purchase #6	$75.87	13.173%	$85.8644	$85.86	$85.85	$85.90
Purchase #7	$201.74	11.409%	$224.7565	$224.76	$224.75	$224.80
7 purchase totals =	$973.77		$1,092.6736	$1,092.68	$1,092.70	$1,092.80