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	$167.36	12.295%	$187.9369	$187.94	$187.95	$187.90
Purchase #2	$220.83	11.797%	$246.8813	$246.88	$246.90	$246.90
Purchase #3	$153.83	5.412%	$162.1553	$162.16	$162.15	$162.20
Purchase #4	$184.46	8.798%	$200.6888	$200.69	$200.70	$200.70
Purchase #5	$22.54	7.700%	$24.2756	$24.28	$24.30	$24.30
Purchase #6	$166.25	12.394%	$186.855	$186.86	$186.85	$186.90
Purchase #7	$47.69	9.374%	$52.1605	$52.16	$52.15	$52.20
7 purchase totals =	$962.96		$1,060.9534	$1,060.97	$1,061.00	$1,061.10