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	$100.71	4.240%	$104.9801	$104.98	$105.00	$105.00
Purchase #2	$233.50	7.399%	$250.7767	$250.78	$250.80	$250.80
Purchase #3	$104.60	6.372%	$111.2651	$111.27	$111.25	$111.30
Purchase #4	$77.93	8.262%	$84.3686	$84.37	$84.35	$84.40
Purchase #5	$136.64	3.490%	$141.4087	$141.41	$141.40	$141.40
Purchase #6	$143.61	9.263%	$156.9126	$156.91	$156.90	$156.90
Purchase #7	$105.48	8.436%	$114.3783	$114.38	$114.40	$114.40
7 purchase totals =	$902.47		$964.0901	$964.10	$964.10	$964.20