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	$146.79	5.177%	$154.3893	$154.39	$154.40	$154.40
Purchase #2	$73.90	5.731%	$78.1352	$78.14	$78.15	$78.10
Purchase #3	$47.95	5.776%	$50.7196	$50.72	$50.70	$50.70
Purchase #4	$19.32	5.640%	$20.4096	$20.41	$20.40	$20.40
Purchase #5	$133.85	8.526%	$145.2621	$145.26	$145.25	$145.30
Purchase #6	$222.61	8.488%	$241.5051	$241.51	$241.50	$241.50
Purchase #7	$84.89	10.651%	$93.9316	$93.93	$93.95	$93.90
7 purchase totals =	$729.31		$784.3525	$784.36	$784.35	$784.30