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	$159.65	7.664%	$171.8856	$171.89	$171.90	$171.90
Purchase #2	$39.78	6.364%	$42.3116	$42.31	$42.30	$42.30
Purchase #3	$154.77	5.721%	$163.6244	$163.62	$163.60	$163.60
Purchase #4	$88.59	11.583%	$98.8514	$98.85	$98.85	$98.90
Purchase #5	$239.93	7.753%	$258.5318	$258.53	$258.55	$258.50
Purchase #6	$199.50	6.197%	$211.863	$211.86	$211.85	$211.90
Purchase #7	$186.59	12.441%	$209.8037	$209.80	$209.80	$209.80
7 purchase totals =	$1,068.81		$1,156.8715	$1,156.86	$1,156.85	$1,156.90