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	$164.64	13.698%	$187.1924	$187.19	$187.20	$187.20
Purchase #2	$175.98	6.238%	$186.9576	$186.96	$186.95	$187.00
Purchase #3	$125.54	10.837%	$139.1448	$139.14	$139.15	$139.10
Purchase #4	$146.34	6.521%	$155.8828	$155.88	$155.90	$155.90
Purchase #5	$149.82	12.669%	$168.8007	$168.80	$168.80	$168.80
Purchase #6	$189.89	5.783%	$200.8713	$200.87	$200.85	$200.90
Purchase #7	$25.86	13.323%	$29.3053	$29.31	$29.30	$29.30
7 purchase totals =	$978.07		$1,068.1549	$1,068.15	$1,068.15	$1,068.20