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	$213.30	4.140%	$222.1306	$222.13	$222.15	$222.10
Purchase #2	$79.78	9.806%	$87.6032	$87.60	$87.60	$87.60
Purchase #3	$171.99	5.760%	$181.8966	$181.90	$181.90	$181.90
Purchase #4	$112.75	13.352%	$127.8044	$127.80	$127.80	$127.80
Purchase #5	$116.73	9.436%	$127.7446	$127.74	$127.75	$127.70
Purchase #6	$12.46	8.370%	$13.5029	$13.50	$13.50	$13.50
Purchase #7	$146.67	13.620%	$166.6465	$166.65	$166.65	$166.60
7 purchase totals =	$853.68		$927.3288	$927.32	$927.35	$927.20