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	$206.73	7.597%	$222.4353	$222.44	$222.45	$222.40
Purchase #2	$143.57	7.488%	$154.3205	$154.32	$154.30	$154.30
Purchase #3	$161.63	12.715%	$182.1813	$182.18	$182.20	$182.20
Purchase #4	$134.38	5.161%	$141.3154	$141.32	$141.30	$141.30
Purchase #5	$63.79	11.532%	$71.1463	$71.15	$71.15	$71.10
Purchase #6	$235.97	3.187%	$243.4904	$243.49	$243.50	$243.50
Purchase #7	$54.54	6.540%	$58.1069	$58.11	$58.10	$58.10
7 purchase totals =	$1,000.61		$1,072.9961	$1,073.01	$1,073.00	$1,072.90