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	$19.98	10.522%	$22.0823	$22.08	$22.10	$22.10
Purchase #2	$150.89	5.497%	$159.1844	$159.18	$159.20	$159.20
Purchase #3	$99.59	9.742%	$109.2921	$109.29	$109.30	$109.30
Purchase #4	$98.65	6.373%	$104.937	$104.94	$104.95	$104.90
Purchase #5	$14.52	4.853%	$15.2247	$15.22	$15.20	$15.20
Purchase #6	$174.87	5.732%	$184.8935	$184.89	$184.90	$184.90
Purchase #7	$143.52	8.609%	$155.8756	$155.88	$155.90	$155.90
7 purchase totals =	$702.02		$751.4896	$751.48	$751.55	$751.50