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	$67.73	8.186%	$73.2744	$73.27	$73.25	$73.30
Purchase #2	$198.32	5.831%	$209.884	$209.88	$209.90	$209.90
Purchase #3	$69.40	10.781%	$76.882	$76.88	$76.90	$76.90
Purchase #4	$33.79	10.767%	$37.4282	$37.43	$37.45	$37.40
Purchase #5	$17.30	9.753%	$18.9873	$18.99	$19.00	$19.00
Purchase #6	$173.89	13.767%	$197.8294	$197.83	$197.85	$197.80
Purchase #7	$69.53	3.737%	$72.1283	$72.13	$72.15	$72.10
7 purchase totals =	$629.96		$686.4136	$686.41	$686.50	$686.40