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	$203.45	4.164%	$211.9217	$211.92	$211.90	$211.90
Purchase #2	$131.27	10.572%	$145.1479	$145.15	$145.15	$145.10
Purchase #3	$11.81	13.689%	$13.4267	$13.43	$13.45	$13.40
Purchase #4	$86.85	4.557%	$90.8078	$90.81	$90.80	$90.80
Purchase #5	$245.95	11.437%	$274.0793	$274.08	$274.10	$274.10
Purchase #6	$218.97	6.149%	$232.4345	$232.43	$232.45	$232.40
Purchase #7	$130.25	4.471%	$136.0735	$136.07	$136.05	$136.10
7 purchase totals =	$1,028.55		$1,103.8914	$1,103.89	$1,103.90	$1,103.80