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	$148.27	5.503%	$156.4293	$156.43	$156.45	$156.40
Purchase #2	$100.46	13.852%	$114.3757	$114.38	$114.40	$114.40
Purchase #3	$167.43	9.780%	$183.8047	$183.80	$183.80	$183.80
Purchase #4	$148.49	13.507%	$168.5465	$168.55	$168.55	$168.50
Purchase #5	$227.48	5.283%	$239.4978	$239.50	$239.50	$239.50
Purchase #6	$79.92	11.231%	$88.8958	$88.90	$88.90	$88.90
Purchase #7	$151.76	13.441%	$172.1581	$172.16	$172.15	$172.20
7 purchase totals =	$1,023.81		$1,123.7079	$1,123.72	$1,123.75	$1,123.70