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	$104.60	4.742%	$109.5601	$109.56	$109.55	$109.60
Purchase #2	$64.46	10.273%	$71.082	$71.08	$71.10	$71.10
Purchase #3	$30.51	9.187%	$33.313	$33.31	$33.30	$33.30
Purchase #4	$213.83	11.541%	$238.5081	$238.51	$238.50	$238.50
Purchase #5	$186.62	4.515%	$195.0459	$195.05	$195.05	$195.00
Purchase #6	$50.86	13.385%	$57.6676	$57.67	$57.65	$57.70
Purchase #7	$71.89	13.813%	$81.8202	$81.82	$81.80	$81.80
7 purchase totals =	$722.77		$786.9969	$787.00	$786.95	$787.00