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	$95.87	4.657%	$100.3347	$100.33	$100.35	$100.30
Purchase #2	$186.72	8.667%	$202.903	$202.90	$202.90	$202.90
Purchase #3	$100.46	13.339%	$113.8604	$113.86	$113.85	$113.90
Purchase #4	$180.60	11.336%	$201.0728	$201.07	$201.05	$201.10
Purchase #5	$33.42	11.545%	$37.2783	$37.28	$37.30	$37.30
Purchase #6	$209.77	7.406%	$225.3056	$225.31	$225.30	$225.30
Purchase #7	$171.30	4.627%	$179.2261	$179.23	$179.25	$179.20
7 purchase totals =	$978.14		$1,059.9809	$1,059.98	$1,060.00	$1,060.00