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	$154.50	5.814%	$163.4826	$163.48	$163.50	$163.50
Purchase #2	$183.30	3.811%	$190.2856	$190.29	$190.30	$190.30
Purchase #3	$229.60	3.778%	$238.2743	$238.27	$238.25	$238.30
Purchase #4	$71.50	9.662%	$78.4083	$78.41	$78.40	$78.40
Purchase #5	$63.58	13.786%	$72.3451	$72.35	$72.35	$72.30
Purchase #6	$17.56	6.415%	$18.6865	$18.69	$18.70	$18.70
Purchase #7	$228.35	10.317%	$251.9089	$251.91	$251.90	$251.90
7 purchase totals =	$948.39		$1,013.3913	$1,013.40	$1,013.40	$1,013.40