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	$160.89	4.385%	$167.945	$167.95	$167.95	$167.90
Purchase #2	$161.52	6.674%	$172.2998	$172.30	$172.30	$172.30
Purchase #3	$198.42	5.275%	$208.8867	$208.89	$208.90	$208.90
Purchase #4	$148.77	9.336%	$162.6592	$162.66	$162.65	$162.70
Purchase #5	$128.64	9.368%	$140.691	$140.69	$140.70	$140.70
Purchase #6	$210.90	13.839%	$240.0865	$240.09	$240.10	$240.10
Purchase #7	$220.49	11.512%	$245.8728	$245.87	$245.85	$245.90
7 purchase totals =	$1,229.63		$1,338.4410	$1,338.45	$1,338.45	$1,338.50