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	$152.84	10.640%	$169.1022	$169.10	$169.10	$169.10
Purchase #2	$79.73	10.155%	$87.8266	$87.83	$87.85	$87.80
Purchase #3	$215.38	3.314%	$222.5177	$222.52	$222.50	$222.50
Purchase #4	$174.88	10.429%	$193.1182	$193.12	$193.10	$193.10
Purchase #5	$118.42	11.659%	$132.2266	$132.23	$132.25	$132.20
Purchase #6	$240.80	10.272%	$265.535	$265.54	$265.55	$265.50
Purchase #7	$9.56	9.652%	$10.4827	$10.48	$10.50	$10.50
7 purchase totals =	$991.61		$1,080.8090	$1,080.82	$1,080.85	$1,080.70