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	$205.44	9.741%	$225.4519	$225.45	$225.45	$225.50
Purchase #2	$63.51	4.420%	$66.3171	$66.32	$66.30	$66.30
Purchase #3	$143.52	4.561%	$150.0659	$150.07	$150.05	$150.10
Purchase #4	$114.57	10.285%	$126.3535	$126.35	$126.35	$126.40
Purchase #5	$87.65	12.215%	$98.3564	$98.36	$98.35	$98.40
Purchase #6	$87.75	3.319%	$90.6624	$90.66	$90.65	$90.70
Purchase #7	$240.28	10.629%	$265.8194	$265.82	$265.80	$265.80
7 purchase totals =	$942.72		$1,023.0266	$1,023.03	$1,022.95	$1,023.20