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	$185.93	10.641%	$205.7148	$205.71	$205.70	$205.70
Purchase #2	$195.77	13.342%	$221.8896	$221.89	$221.90	$221.90
Purchase #3	$206.68	10.501%	$228.3835	$228.38	$228.40	$228.40
Purchase #4	$65.37	11.107%	$72.6306	$72.63	$72.65	$72.60
Purchase #5	$83.53	6.744%	$89.1633	$89.16	$89.15	$89.20
Purchase #6	$51.64	8.861%	$56.2158	$56.22	$56.20	$56.20
Purchase #7	$209.78	3.197%	$216.4867	$216.49	$216.50	$216.50
7 purchase totals =	$998.70		$1,090.4843	$1,090.48	$1,090.50	$1,090.50