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	$172.33	3.725%	$178.7493	$178.75	$178.75	$178.70
Purchase #2	$169.99	12.565%	$191.3492	$191.35	$191.35	$191.30
Purchase #3	$133.26	8.351%	$144.3885	$144.39	$144.40	$144.40
Purchase #4	$227.83	11.667%	$254.4109	$254.41	$254.40	$254.40
Purchase #5	$40.49	13.414%	$45.9213	$45.92	$45.90	$45.90
Purchase #6	$55.46	7.217%	$59.4625	$59.46	$59.45	$59.50
Purchase #7	$188.33	12.771%	$212.3816	$212.38	$212.40	$212.40
7 purchase totals =	$987.69		$1,086.6633	$1,086.66	$1,086.65	$1,086.60