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	$178.35	12.656%	$200.922	$200.92	$200.90	$200.90
Purchase #2	$25.70	8.438%	$27.8686	$27.87	$27.85	$27.90
Purchase #3	$210.97	5.160%	$221.8561	$221.86	$221.85	$221.90
Purchase #4	$88.59	3.199%	$91.424	$91.42	$91.40	$91.40
Purchase #5	$78.48	12.608%	$88.3748	$88.37	$88.35	$88.40
Purchase #6	$210.86	3.569%	$218.3856	$218.39	$218.40	$218.40
Purchase #7	$227.65	8.514%	$247.0321	$247.03	$247.05	$247.00
7 purchase totals =	$1,020.60		$1,095.8632	$1,095.86	$1,095.80	$1,095.90