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	$83.91	13.373%	$95.1313	$95.13	$95.15	$95.10
Purchase #2	$31.32	9.498%	$34.2948	$34.29	$34.30	$34.30
Purchase #3	$64.66	12.483%	$72.7315	$72.73	$72.75	$72.70
Purchase #4	$146.32	4.397%	$152.7537	$152.75	$152.75	$152.80
Purchase #5	$191.77	12.351%	$215.4555	$215.46	$215.45	$215.50
Purchase #6	$18.69	9.690%	$20.5011	$20.50	$20.50	$20.50
Purchase #7	$79.82	13.638%	$90.7059	$90.71	$90.70	$90.70
7 purchase totals =	$616.49		$681.5738	$681.57	$681.60	$681.60