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	$58.73	13.753%	$66.8071	$66.81	$66.80	$66.80
Purchase #2	$99.46	5.584%	$105.0138	$105.01	$105.00	$105.00
Purchase #3	$176.34	13.657%	$200.4228	$200.42	$200.40	$200.40
Purchase #4	$186.53	13.627%	$211.9484	$211.95	$211.95	$211.90
Purchase #5	$218.72	6.330%	$232.565	$232.57	$232.55	$232.60
Purchase #6	$240.73	10.176%	$265.2267	$265.23	$265.25	$265.20
Purchase #7	$147.85	3.424%	$152.9124	$152.91	$152.90	$152.90
7 purchase totals =	$1,128.36		$1,234.8962	$1,234.90	$1,234.85	$1,234.80