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	$250.86	12.415%	$282.0043	$282.00	$282.00	$282.00
Purchase #2	$107.45	12.530%	$120.9135	$120.91	$120.90	$120.90
Purchase #3	$115.49	7.326%	$123.9508	$123.95	$123.95	$124.00
Purchase #4	$153.38	5.761%	$162.2162	$162.22	$162.20	$162.20
Purchase #5	$90.40	9.345%	$98.8479	$98.85	$98.85	$98.80
Purchase #6	$120.32	9.295%	$131.5037	$131.50	$131.50	$131.50
Purchase #7	$186.47	5.407%	$196.5524	$196.55	$196.55	$196.60
7 purchase totals =	$1,024.37		$1,115.9888	$1,115.98	$1,115.95	$1,116.00