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	$216.58	13.299%	$245.383	$245.38	$245.40	$245.40
Purchase #2	$134.65	5.467%	$142.0113	$142.01	$142.00	$142.00
Purchase #3	$74.33	11.122%	$82.597	$82.60	$82.60	$82.60
Purchase #4	$227.44	9.162%	$248.2781	$248.28	$248.30	$248.30
Purchase #5	$116.25	12.402%	$130.6673	$130.67	$130.65	$130.70
Purchase #6	$241.48	13.303%	$273.6041	$273.60	$273.60	$273.60
Purchase #7	$130.57	11.870%	$146.0687	$146.07	$146.05	$146.10
7 purchase totals =	$1,141.30		$1,268.6095	$1,268.61	$1,268.60	$1,268.70