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	$128.59	9.764%	$141.1455	$141.15	$141.15	$141.10
Purchase #2	$36.87	13.481%	$41.8404	$41.84	$41.85	$41.80
Purchase #3	$80.55	5.547%	$85.0181	$85.02	$85.00	$85.00
Purchase #4	$173.95	4.412%	$181.6247	$181.62	$181.60	$181.60
Purchase #5	$38.60	9.178%	$42.1427	$42.14	$42.15	$42.10
Purchase #6	$98.42	7.538%	$105.8389	$105.84	$105.85	$105.80
Purchase #7	$33.80	9.833%	$37.1236	$37.12	$37.10	$37.10
7 purchase totals =	$590.78		$634.7339	$634.73	$634.70	$634.50