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	$218.45	13.402%	$247.7267	$247.73	$247.75	$247.70
Purchase #2	$97.75	10.318%	$107.8358	$107.84	$107.85	$107.80
Purchase #3	$168.41	5.351%	$177.4216	$177.42	$177.40	$177.40
Purchase #4	$174.47	12.586%	$196.4288	$196.43	$196.45	$196.40
Purchase #5	$51.27	6.834%	$54.7738	$54.77	$54.75	$54.80
Purchase #6	$143.76	11.660%	$160.5224	$160.52	$160.50	$160.50
Purchase #7	$76.90	12.247%	$86.3179	$86.32	$86.30	$86.30
7 purchase totals =	$931.01		$1,031.0270	$1,031.03	$1,031.00	$1,030.90