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	$248.74	10.850%	$275.7283	$275.73	$275.75	$275.70
Purchase #2	$249.45	12.472%	$280.5614	$280.56	$280.55	$280.60
Purchase #3	$47.52	10.554%	$52.5353	$52.54	$52.55	$52.50
Purchase #4	$188.44	12.176%	$211.3845	$211.38	$211.40	$211.40
Purchase #5	$26.38	11.786%	$29.4891	$29.49	$29.50	$29.50
Purchase #6	$167.44	3.138%	$172.6943	$172.69	$172.70	$172.70
Purchase #7	$115.54	5.220%	$121.5712	$121.57	$121.55	$121.60
7 purchase totals =	$1,043.51		$1,143.9641	$1,143.96	$1,144.00	$1,144.00