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	$104.85	4.370%	$109.4319	$109.43	$109.45	$109.40
Purchase #2	$34.70	11.784%	$38.789	$38.79	$38.80	$38.80
Purchase #3	$120.42	10.610%	$133.1966	$133.20	$133.20	$133.20
Purchase #4	$38.35	11.412%	$42.7265	$42.73	$42.75	$42.70
Purchase #5	$180.59	3.802%	$187.456	$187.46	$187.45	$187.50
Purchase #6	$64.75	11.870%	$72.4358	$72.44	$72.45	$72.40
Purchase #7	$164.68	3.704%	$170.7797	$170.78	$170.80	$170.80
7 purchase totals =	$708.34		$754.8155	$754.83	$754.90	$754.80