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	$98.53	11.777%	$110.1339	$110.13	$110.15	$110.10
Purchase #2	$22.93	10.696%	$25.3826	$25.38	$25.40	$25.40
Purchase #3	$104.33	13.591%	$118.5095	$118.51	$118.50	$118.50
Purchase #4	$88.35	13.452%	$100.2348	$100.23	$100.25	$100.20
Purchase #5	$53.34	7.714%	$57.4546	$57.45	$57.45	$57.50
Purchase #6	$75.66	8.538%	$82.1199	$82.12	$82.10	$82.10
Purchase #7	$168.63	12.133%	$189.0899	$189.09	$189.10	$189.10
7 purchase totals =	$611.77		$682.9252	$682.91	$682.95	$682.90