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	$52.73	4.500%	$55.1029	$55.10	$55.10	$55.10
Purchase #2	$119.58	3.487%	$123.7498	$123.75	$123.75	$123.70
Purchase #3	$127.92	7.131%	$137.042	$137.04	$137.05	$137.00
Purchase #4	$193.58	13.614%	$219.934	$219.93	$219.95	$219.90
Purchase #5	$142.76	12.872%	$161.1361	$161.14	$161.15	$161.10
Purchase #6	$163.83	5.280%	$172.4802	$172.48	$172.50	$172.50
Purchase #7	$100.56	4.324%	$104.9082	$104.91	$104.90	$104.90
7 purchase totals =	$900.96		$974.3532	$974.35	$974.40	$974.20