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	$127.64	7.793%	$137.587	$137.59	$137.60	$137.60
Purchase #2	$49.47	6.787%	$52.8275	$52.83	$52.85	$52.80
Purchase #3	$79.51	10.336%	$87.7282	$87.73	$87.75	$87.70
Purchase #4	$63.43	6.244%	$67.3906	$67.39	$67.40	$67.40
Purchase #5	$229.49	9.234%	$250.6811	$250.68	$250.70	$250.70
Purchase #6	$138.51	13.225%	$156.8279	$156.83	$156.85	$156.80
Purchase #7	$145.72	11.631%	$162.6687	$162.67	$162.65	$162.70
7 purchase totals =	$833.77		$915.7110	$915.72	$915.80	$915.70