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	$92.65	11.659%	$103.4521	$103.45	$103.45	$103.50
Purchase #2	$28.98	8.345%	$31.3984	$31.40	$31.40	$31.40
Purchase #3	$157.46	10.647%	$174.2248	$174.22	$174.20	$174.20
Purchase #4	$29.83	12.565%	$33.5781	$33.58	$33.60	$33.60
Purchase #5	$249.40	11.155%	$277.2206	$277.22	$277.20	$277.20
Purchase #6	$213.85	7.244%	$229.3413	$229.34	$229.35	$229.30
Purchase #7	$104.66	4.820%	$109.7046	$109.70	$109.70	$109.70
7 purchase totals =	$876.83		$958.9199	$958.91	$958.90	$958.90