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	$210.77	7.790%	$227.189	$227.19	$227.20	$227.20
Purchase #2	$162.92	6.169%	$172.9705	$172.97	$172.95	$173.00
Purchase #3	$228.53	6.665%	$243.7615	$243.76	$243.75	$243.80
Purchase #4	$200.46	10.466%	$221.4401	$221.44	$221.45	$221.40
Purchase #5	$106.66	8.407%	$115.6269	$115.63	$115.65	$115.60
Purchase #6	$109.38	12.870%	$123.4572	$123.46	$123.45	$123.50
Purchase #7	$42.70	11.410%	$47.5721	$47.57	$47.55	$47.60
7 purchase totals =	$1,061.42		$1,152.0173	$1,152.02	$1,152.00	$1,152.10