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	$172.64	11.116%	$191.8307	$191.83	$191.85	$191.80
Purchase #2	$138.57	10.841%	$153.5924	$153.59	$153.60	$153.60
Purchase #3	$247.41	13.178%	$280.0137	$280.01	$280.00	$280.00
Purchase #4	$28.88	8.410%	$31.3088	$31.31	$31.30	$31.30
Purchase #5	$34.47	8.427%	$37.3748	$37.37	$37.35	$37.40
Purchase #6	$162.66	7.502%	$174.8628	$174.86	$174.85	$174.90
Purchase #7	$189.32	12.697%	$213.358	$213.36	$213.35	$213.40
7 purchase totals =	$973.95		$1,082.3412	$1,082.33	$1,082.30	$1,082.40