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	$189.40	3.494%	$196.0176	$196.02	$196.00	$196.00
Purchase #2	$183.70	4.665%	$192.2696	$192.27	$192.25	$192.30
Purchase #3	$145.34	6.636%	$154.9848	$154.98	$155.00	$155.00
Purchase #4	$130.35	7.208%	$139.7456	$139.75	$139.75	$139.70
Purchase #5	$108.71	8.127%	$117.5449	$117.54	$117.55	$117.50
Purchase #6	$57.35	7.828%	$61.8394	$61.84	$61.85	$61.80
Purchase #7	$173.97	8.340%	$188.4791	$188.48	$188.50	$188.50
7 purchase totals =	$988.82		$1,050.8810	$1,050.88	$1,050.90	$1,050.80