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	$221.78	13.639%	$252.0286	$252.03	$252.05	$252.00
Purchase #2	$170.73	6.254%	$181.4075	$181.41	$181.40	$181.40
Purchase #3	$27.88	12.746%	$31.4336	$31.43	$31.45	$31.40
Purchase #4	$250.40	4.632%	$261.9985	$262.00	$262.00	$262.00
Purchase #5	$148.36	11.565%	$165.5178	$165.52	$165.50	$165.50
Purchase #6	$78.51	13.788%	$89.335	$89.34	$89.35	$89.30
Purchase #7	$157.93	7.701%	$170.0922	$170.09	$170.10	$170.10
7 purchase totals =	$1,055.59		$1,151.8132	$1,151.82	$1,151.85	$1,151.70