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	$136.63	7.717%	$147.1737	$147.17	$147.15	$147.20
Purchase #2	$127.56	13.482%	$144.7576	$144.76	$144.75	$144.80
Purchase #3	$152.82	8.495%	$165.8021	$165.80	$165.80	$165.80
Purchase #4	$207.60	5.190%	$218.3744	$218.37	$218.35	$218.40
Purchase #5	$142.82	4.276%	$148.927	$148.93	$148.95	$148.90
Purchase #6	$201.57	4.109%	$209.8525	$209.85	$209.85	$209.90
Purchase #7	$160.92	11.528%	$179.4709	$179.47	$179.45	$179.50
7 purchase totals =	$1,129.92		$1,214.3582	$1,214.35	$1,214.30	$1,214.50