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	$145.56	11.521%	$162.33	$162.33	$162.35	$162.30
Purchase #2	$232.64	5.483%	$245.3957	$245.40	$245.40	$245.40
Purchase #3	$215.83	5.229%	$227.1158	$227.12	$227.10	$227.10
Purchase #4	$69.42	7.574%	$74.6779	$74.68	$74.70	$74.70
Purchase #5	$19.53	8.874%	$21.2631	$21.26	$21.25	$21.30
Purchase #6	$213.68	4.283%	$222.8319	$222.83	$222.85	$222.80
Purchase #7	$136.30	7.487%	$146.5048	$146.50	$146.50	$146.50
7 purchase totals =	$1,032.96		$1,100.1192	$1,100.12	$1,100.15	$1,100.10