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	$103.68	9.467%	$113.4954	$113.50	$113.50	$113.50
Purchase #2	$217.95	4.206%	$227.117	$227.12	$227.10	$227.10
Purchase #3	$87.28	3.594%	$90.4168	$90.42	$90.40	$90.40
Purchase #4	$223.37	12.131%	$250.467	$250.47	$250.45	$250.50
Purchase #5	$143.32	6.550%	$152.7075	$152.71	$152.70	$152.70
Purchase #6	$91.61	7.797%	$98.7528	$98.75	$98.75	$98.80
Purchase #7	$185.40	4.148%	$193.0904	$193.09	$193.10	$193.10
7 purchase totals =	$1,052.61		$1,126.0469	$1,126.06	$1,126.00	$1,126.10