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	$120.71	5.530%	$127.3853	$127.39	$127.40	$127.40
Purchase #2	$70.82	13.713%	$80.5315	$80.53	$80.55	$80.50
Purchase #3	$45.68	4.771%	$47.8594	$47.86	$47.85	$47.90
Purchase #4	$206.92	6.314%	$219.9849	$219.98	$220.00	$220.00
Purchase #5	$30.94	4.466%	$32.3218	$32.32	$32.30	$32.30
Purchase #6	$54.88	13.540%	$62.3108	$62.31	$62.30	$62.30
Purchase #7	$123.64	10.790%	$136.9808	$136.98	$137.00	$137.00
7 purchase totals =	$653.59		$707.3745	$707.37	$707.40	$707.40