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	$101.45	3.585%	$105.087	$105.09	$105.10	$105.10
Purchase #2	$113.85	9.133%	$124.2479	$124.25	$124.25	$124.20
Purchase #3	$132.92	8.418%	$144.1092	$144.11	$144.10	$144.10
Purchase #4	$101.64	8.169%	$109.943	$109.94	$109.95	$109.90
Purchase #5	$245.43	4.120%	$255.5417	$255.54	$255.55	$255.50
Purchase #6	$211.65	12.394%	$237.8819	$237.88	$237.90	$237.90
Purchase #7	$125.28	4.467%	$130.8763	$130.88	$130.90	$130.90
7 purchase totals =	$1,032.22		$1,107.6870	$1,107.69	$1,107.75	$1,107.60