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	$206.30	8.414%	$223.6581	$223.66	$223.65	$223.70
Purchase #2	$21.91	5.107%	$23.0289	$23.03	$23.05	$23.00
Purchase #3	$75.29	4.181%	$78.4379	$78.44	$78.45	$78.40
Purchase #4	$83.46	11.110%	$92.7324	$92.73	$92.75	$92.70
Purchase #5	$141.69	10.735%	$156.9004	$156.90	$156.90	$156.90
Purchase #6	$150.43	10.530%	$166.2703	$166.27	$166.25	$166.30
Purchase #7	$178.54	5.525%	$188.4043	$188.40	$188.40	$188.40
7 purchase totals =	$857.62		$929.4323	$929.43	$929.45	$929.40