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	$63.54	13.862%	$72.3479	$72.35	$72.35	$72.30
Purchase #2	$102.25	7.145%	$109.5558	$109.56	$109.55	$109.60
Purchase #3	$198.63	10.406%	$219.2994	$219.30	$219.30	$219.30
Purchase #4	$49.33	12.210%	$55.3532	$55.35	$55.35	$55.40
Purchase #5	$190.52	8.416%	$206.5542	$206.55	$206.55	$206.60
Purchase #6	$95.68	5.675%	$101.1098	$101.11	$101.10	$101.10
Purchase #7	$142.44	11.273%	$158.4973	$158.50	$158.50	$158.50
7 purchase totals =	$842.39		$922.7176	$922.72	$922.70	$922.80