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	$181.78	10.285%	$200.4761	$200.48	$200.50	$200.50
Purchase #2	$220.73	8.777%	$240.1035	$240.10	$240.10	$240.10
Purchase #3	$163.94	4.639%	$171.5452	$171.55	$171.55	$171.50
Purchase #4	$127.99	6.668%	$136.5244	$136.52	$136.50	$136.50
Purchase #5	$99.37	6.359%	$105.6889	$105.69	$105.70	$105.70
Purchase #6	$95.88	10.320%	$105.7748	$105.77	$105.75	$105.80
Purchase #7	$105.36	4.763%	$110.3783	$110.38	$110.40	$110.40
7 purchase totals =	$995.05		$1,070.4912	$1,070.49	$1,070.50	$1,070.50