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	$24.33	3.610%	$25.2083	$25.21	$25.20	$25.20
Purchase #2	$42.29	10.831%	$46.8704	$46.87	$46.85	$46.90
Purchase #3	$62.50	4.761%	$65.4756	$65.48	$65.50	$65.50
Purchase #4	$101.39	7.513%	$109.0074	$109.01	$109.00	$109.00
Purchase #5	$7.37	3.120%	$7.5999	$7.60	$7.60	$7.60
Purchase #6	$115.84	10.268%	$127.7345	$127.73	$127.75	$127.70
Purchase #7	$28.94	5.127%	$30.4238	$30.42	$30.40	$30.40
7 purchase totals =	$382.66		$412.3199	$412.32	$412.30	$412.30