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	$77.31	5.268%	$81.3827	$81.38	$81.40	$81.40
Purchase #2	$232.54	8.246%	$251.7152	$251.72	$251.70	$251.70
Purchase #3	$119.89	3.302%	$123.8488	$123.85	$123.85	$123.80
Purchase #4	$215.56	7.111%	$230.8885	$230.89	$230.90	$230.90
Purchase #5	$93.48	6.144%	$99.2234	$99.22	$99.20	$99.20
Purchase #6	$51.71	3.829%	$53.69	$53.69	$53.70	$53.70
Purchase #7	$232.91	9.821%	$255.7841	$255.78	$255.80	$255.80
7 purchase totals =	$1,023.40		$1,096.5327	$1,096.53	$1,096.55	$1,096.50