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	$176.47	11.420%	$196.6229	$196.62	$196.60	$196.60
Purchase #2	$217.60	3.840%	$225.9558	$225.96	$225.95	$226.00
Purchase #3	$77.57	3.832%	$80.5425	$80.54	$80.55	$80.50
Purchase #4	$94.49	4.783%	$99.0095	$99.01	$99.00	$99.00
Purchase #5	$206.45	11.744%	$230.6955	$230.70	$230.70	$230.70
Purchase #6	$99.74	6.704%	$106.4266	$106.43	$106.45	$106.40
Purchase #7	$128.32	11.104%	$142.5687	$142.57	$142.55	$142.60
7 purchase totals =	$1,000.64		$1,081.8215	$1,081.83	$1,081.80	$1,081.80