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	$122.28	4.137%	$127.3387	$127.34	$127.35	$127.30
Purchase #2	$238.43	8.212%	$258.0099	$258.01	$258.00	$258.00
Purchase #3	$158.69	10.362%	$175.1335	$175.13	$175.15	$175.10
Purchase #4	$243.39	8.562%	$264.2291	$264.23	$264.25	$264.20
Purchase #5	$74.94	5.191%	$78.8301	$78.83	$78.85	$78.80
Purchase #6	$115.54	6.659%	$123.2338	$123.23	$123.25	$123.20
Purchase #7	$78.94	4.531%	$82.5168	$82.52	$82.50	$82.50
7 purchase totals =	$1,032.21		$1,109.2919	$1,109.29	$1,109.35	$1,109.10