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	$53.73	7.635%	$57.8323	$57.83	$57.85	$57.80
Purchase #2	$101.98	9.828%	$112.0026	$112.00	$112.00	$112.00
Purchase #3	$97.63	3.336%	$100.8869	$100.89	$100.90	$100.90
Purchase #4	$245.42	10.636%	$271.5229	$271.52	$271.50	$271.50
Purchase #5	$38.56	4.847%	$40.429	$40.43	$40.45	$40.40
Purchase #6	$131.45	7.634%	$141.4849	$141.48	$141.50	$141.50
Purchase #7	$197.26	3.134%	$203.4421	$203.44	$203.45	$203.40
7 purchase totals =	$866.03		$927.6007	$927.59	$927.65	$927.50