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	$85.73	5.540%	$90.4794	$90.48	$90.50	$90.50
Purchase #2	$197.45	8.468%	$214.1701	$214.17	$214.15	$214.20
Purchase #3	$124.38	5.562%	$131.298	$131.30	$131.30	$131.30
Purchase #4	$165.36	8.443%	$179.3213	$179.32	$179.30	$179.30
Purchase #5	$11.80	4.351%	$12.3134	$12.31	$12.30	$12.30
Purchase #6	$189.94	7.365%	$203.9291	$203.93	$203.95	$203.90
Purchase #7	$200.90	7.275%	$215.5155	$215.52	$215.50	$215.50
7 purchase totals =	$975.56		$1,047.0268	$1,047.03	$1,047.00	$1,047.00