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	$70.56	3.117%	$72.7594	$72.76	$72.75	$72.80
Purchase #2	$190.83	7.710%	$205.543	$205.54	$205.55	$205.50
Purchase #3	$202.48	11.474%	$225.7126	$225.71	$225.70	$225.70
Purchase #4	$49.77	4.789%	$52.1535	$52.15	$52.15	$52.20
Purchase #5	$118.34	4.259%	$123.3801	$123.38	$123.40	$123.40
Purchase #6	$169.74	10.106%	$186.8939	$186.89	$186.90	$186.90
Purchase #7	$139.40	3.322%	$144.0309	$144.03	$144.05	$144.00
7 purchase totals =	$941.12		$1,010.4734	$1,010.46	$1,010.50	$1,010.50