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	$185.69	5.756%	$196.3783	$196.38	$196.40	$196.40
Purchase #2	$51.32	12.389%	$57.678	$57.68	$57.70	$57.70
Purchase #3	$25.54	5.452%	$26.9324	$26.93	$26.95	$26.90
Purchase #4	$60.45	11.788%	$67.5758	$67.58	$67.60	$67.60
Purchase #5	$167.66	3.744%	$173.9372	$173.94	$173.95	$173.90
Purchase #6	$171.35	3.672%	$177.642	$177.64	$177.65	$177.60
Purchase #7	$105.26	3.705%	$109.1599	$109.16	$109.15	$109.20
7 purchase totals =	$767.27		$809.3036	$809.31	$809.40	$809.30