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	$105.41	6.687%	$112.4588	$112.46	$112.45	$112.50
Purchase #2	$210.94	4.574%	$220.5884	$220.59	$220.60	$220.60
Purchase #3	$219.47	7.742%	$236.4614	$236.46	$236.45	$236.50
Purchase #4	$190.77	10.868%	$211.5029	$211.50	$211.50	$211.50
Purchase #5	$133.46	6.404%	$142.0068	$142.01	$142.00	$142.00
Purchase #6	$204.43	8.605%	$222.0212	$222.02	$222.00	$222.00
Purchase #7	$221.77	11.560%	$247.4066	$247.41	$247.40	$247.40
7 purchase totals =	$1,286.25		$1,392.4461	$1,392.45	$1,392.40	$1,392.50