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	$103.90	4.809%	$108.8966	$108.90	$108.90	$108.90
Purchase #2	$178.38	7.337%	$191.4677	$191.47	$191.45	$191.50
Purchase #3	$85.42	4.391%	$89.1708	$89.17	$89.15	$89.20
Purchase #4	$248.51	5.752%	$262.8043	$262.80	$262.80	$262.80
Purchase #5	$193.36	3.365%	$199.8666	$199.87	$199.85	$199.90
Purchase #6	$71.52	11.261%	$79.5739	$79.57	$79.55	$79.60
Purchase #7	$73.71	7.179%	$79.0016	$79.00	$79.00	$79.00
7 purchase totals =	$954.80		$1,010.7815	$1,010.78	$1,010.70	$1,010.90