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	$90.83	4.836%	$95.2225	$95.22	$95.20	$95.20
Purchase #2	$225.85	11.129%	$250.9848	$250.98	$251.00	$251.00
Purchase #3	$11.56	5.444%	$12.1893	$12.19	$12.20	$12.20
Purchase #4	$213.89	3.553%	$221.4895	$221.49	$221.50	$221.50
Purchase #5	$157.78	13.537%	$179.1387	$179.14	$179.15	$179.10
Purchase #6	$176.96	7.320%	$189.9135	$189.91	$189.90	$189.90
Purchase #7	$242.87	12.627%	$273.5372	$273.54	$273.55	$273.50
7 purchase totals =	$1,119.74		$1,222.4755	$1,222.47	$1,222.50	$1,222.40