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	$200.45	13.646%	$227.8034	$227.80	$227.80	$227.80
Purchase #2	$101.41	11.708%	$113.2831	$113.28	$113.30	$113.30
Purchase #3	$59.87	5.818%	$63.3532	$63.35	$63.35	$63.40
Purchase #4	$235.47	5.661%	$248.8	$248.80	$248.80	$248.80
Purchase #5	$95.60	5.263%	$100.6314	$100.63	$100.65	$100.60
Purchase #6	$244.49	11.405%	$272.3741	$272.37	$272.35	$272.40
Purchase #7	$58.89	11.237%	$65.5075	$65.51	$65.50	$65.50
7 purchase totals =	$996.18		$1,091.7527	$1,091.74	$1,091.75	$1,091.80