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	$171.40	4.355%	$178.8645	$178.86	$178.85	$178.90
Purchase #2	$32.26	10.297%	$35.5818	$35.58	$35.60	$35.60
Purchase #3	$33.36	12.528%	$37.5393	$37.54	$37.55	$37.50
Purchase #4	$133.78	4.249%	$139.4643	$139.46	$139.45	$139.50
Purchase #5	$68.28	10.467%	$75.4269	$75.43	$75.45	$75.40
Purchase #6	$45.66	6.439%	$48.6	$48.60	$48.60	$48.60
Purchase #7	$213.80	10.280%	$235.7786	$235.78	$235.80	$235.80
7 purchase totals =	$698.54		$751.2554	$751.25	$751.30	$751.30