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	$210.84	13.211%	$238.6941	$238.69	$238.70	$238.70
Purchase #2	$186.35	10.801%	$206.4777	$206.48	$206.50	$206.50
Purchase #3	$112.27	13.425%	$127.3422	$127.34	$127.35	$127.30
Purchase #4	$155.57	6.652%	$165.9185	$165.92	$165.90	$165.90
Purchase #5	$59.71	13.418%	$67.7219	$67.72	$67.70	$67.70
Purchase #6	$59.44	3.398%	$61.4598	$61.46	$61.45	$61.50
Purchase #7	$237.70	3.237%	$245.3943	$245.39	$245.40	$245.40
7 purchase totals =	$1,021.88		$1,113.0085	$1,113.00	$1,113.00	$1,113.00