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	$186.37	12.575%	$209.806	$209.81	$209.80	$209.80
Purchase #2	$39.79	11.292%	$44.2831	$44.28	$44.30	$44.30
Purchase #3	$214.97	3.494%	$222.4811	$222.48	$222.50	$222.50
Purchase #4	$29.32	8.447%	$31.7967	$31.80	$31.80	$31.80
Purchase #5	$139.44	4.390%	$145.5614	$145.56	$145.55	$145.60
Purchase #6	$250.98	11.123%	$278.8965	$278.90	$278.90	$278.90
Purchase #7	$180.45	7.603%	$194.1696	$194.17	$194.15	$194.20
7 purchase totals =	$1,041.32		$1,126.9944	$1,127.00	$1,127.00	$1,127.10