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	$29.38	6.824%	$31.3849	$31.38	$31.40	$31.40
Purchase #2	$31.49	4.331%	$32.8538	$32.85	$32.85	$32.90
Purchase #3	$22.31	7.494%	$23.9819	$23.98	$24.00	$24.00
Purchase #4	$124.72	9.288%	$136.304	$136.30	$136.30	$136.30
Purchase #5	$200.41	4.163%	$208.7531	$208.75	$208.75	$208.80
Purchase #6	$76.50	7.556%	$82.2803	$82.28	$82.30	$82.30
Purchase #7	$165.83	5.433%	$174.8395	$174.84	$174.85	$174.80
7 purchase totals =	$650.64		$690.3975	$690.38	$690.45	$690.50