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	$123.94	3.506%	$128.2853	$128.29	$128.30	$128.30
Purchase #2	$227.41	11.861%	$254.3831	$254.38	$254.40	$254.40
Purchase #3	$32.92	6.126%	$34.9367	$34.94	$34.95	$34.90
Purchase #4	$247.36	10.667%	$273.7459	$273.75	$273.75	$273.70
Purchase #5	$98.53	3.650%	$102.1263	$102.13	$102.15	$102.10
Purchase #6	$166.45	11.517%	$185.62	$185.62	$185.60	$185.60
Purchase #7	$179.28	11.285%	$199.5117	$199.51	$199.50	$199.50
7 purchase totals =	$1,075.89		$1,178.6090	$1,178.62	$1,178.65	$1,178.50