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	$200.42	4.435%	$209.3086	$209.31	$209.30	$209.30
Purchase #2	$42.57	7.236%	$45.6504	$45.65	$45.65	$45.70
Purchase #3	$49.93	6.201%	$53.0262	$53.03	$53.05	$53.00
Purchase #4	$134.67	4.120%	$140.2184	$140.22	$140.20	$140.20
Purchase #5	$166.33	9.623%	$182.3359	$182.34	$182.35	$182.30
Purchase #6	$16.28	13.380%	$18.4583	$18.46	$18.45	$18.50
Purchase #7	$90.87	13.518%	$103.1538	$103.15	$103.15	$103.20
7 purchase totals =	$701.07		$752.1516	$752.16	$752.15	$752.20