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	$90.83	11.736%	$101.4898	$101.49	$101.50	$101.50
Purchase #2	$7.62	3.516%	$7.8879	$7.89	$7.90	$7.90
Purchase #3	$109.75	12.704%	$123.6926	$123.69	$123.70	$123.70
Purchase #4	$209.84	13.405%	$237.9691	$237.97	$237.95	$238.00
Purchase #5	$50.92	3.171%	$52.5347	$52.53	$52.55	$52.50
Purchase #6	$216.56	4.857%	$227.0783	$227.08	$227.10	$227.10
Purchase #7	$194.89	12.488%	$219.2279	$219.23	$219.25	$219.20
7 purchase totals =	$880.41		$969.8803	$969.88	$969.95	$969.90