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	$63.46	13.120%	$71.786	$71.79	$71.80	$71.80
Purchase #2	$81.77	9.116%	$89.2242	$89.22	$89.20	$89.20
Purchase #3	$66.83	3.372%	$69.0835	$69.08	$69.10	$69.10
Purchase #4	$88.91	4.223%	$92.6647	$92.66	$92.65	$92.70
Purchase #5	$50.66	8.249%	$54.8389	$54.84	$54.85	$54.80
Purchase #6	$131.57	11.294%	$146.4295	$146.43	$146.45	$146.40
Purchase #7	$224.32	5.355%	$236.3323	$236.33	$236.35	$236.30
7 purchase totals =	$707.52		$760.3591	$760.35	$760.40	$760.30