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	$242.89	3.252%	$250.7888	$250.79	$250.80	$250.80
Purchase #2	$63.51	3.105%	$65.482	$65.48	$65.50	$65.50
Purchase #3	$96.29	13.330%	$109.1255	$109.13	$109.15	$109.10
Purchase #4	$237.66	10.234%	$261.9821	$261.98	$262.00	$262.00
Purchase #5	$75.69	7.653%	$81.4826	$81.48	$81.50	$81.50
Purchase #6	$168.41	11.111%	$187.122	$187.12	$187.10	$187.10
Purchase #7	$99.50	5.278%	$104.7516	$104.75	$104.75	$104.80
7 purchase totals =	$983.95		$1,060.7346	$1,060.73	$1,060.80	$1,060.80