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	$33.73	10.455%	$37.2565	$37.26	$37.25	$37.30
Purchase #2	$76.80	4.315%	$80.1139	$80.11	$80.10	$80.10
Purchase #3	$40.60	3.633%	$42.075	$42.08	$42.10	$42.10
Purchase #4	$96.97	8.375%	$105.0912	$105.09	$105.10	$105.10
Purchase #5	$104.32	8.825%	$113.5262	$113.53	$113.55	$113.50
Purchase #6	$33.86	4.269%	$35.3055	$35.31	$35.30	$35.30
Purchase #7	$226.50	7.609%	$243.7344	$243.73	$243.75	$243.70
7 purchase totals =	$612.78		$657.1027	$657.11	$657.15	$657.10