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	$142.92	11.175%	$158.8913	$158.89	$158.90	$158.90
Purchase #2	$176.68	3.444%	$182.7649	$182.76	$182.75	$182.80
Purchase #3	$187.31	13.449%	$212.5013	$212.50	$212.50	$212.50
Purchase #4	$40.92	3.520%	$42.3604	$42.36	$42.35	$42.40
Purchase #5	$183.65	5.616%	$193.9638	$193.96	$193.95	$194.00
Purchase #6	$148.54	6.434%	$158.0971	$158.10	$158.10	$158.10
Purchase #7	$185.27	5.734%	$195.8934	$195.89	$195.90	$195.90
7 purchase totals =	$1,065.29		$1,144.4722	$1,144.46	$1,144.45	$1,144.60