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	$104.78	3.215%	$108.1487	$108.15	$108.15	$108.10
Purchase #2	$11.33	13.731%	$12.8857	$12.89	$12.90	$12.90
Purchase #3	$218.90	11.156%	$243.3205	$243.32	$243.30	$243.30
Purchase #4	$76.35	8.552%	$82.8795	$82.88	$82.90	$82.90
Purchase #5	$126.31	8.146%	$136.5992	$136.60	$136.60	$136.60
Purchase #6	$115.92	4.275%	$120.8756	$120.88	$120.90	$120.90
Purchase #7	$153.76	7.400%	$165.1382	$165.14	$165.15	$165.10
7 purchase totals =	$807.35		$869.8474	$869.86	$869.90	$869.80