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	$245.73	11.279%	$273.4459	$273.45	$273.45	$273.40
Purchase #2	$174.87	7.372%	$187.7614	$187.76	$187.75	$187.80
Purchase #3	$160.58	10.395%	$177.2723	$177.27	$177.25	$177.30
Purchase #4	$11.71	12.748%	$13.2028	$13.20	$13.20	$13.20
Purchase #5	$69.30	9.417%	$75.826	$75.83	$75.85	$75.80
Purchase #6	$98.85	12.451%	$111.1578	$111.16	$111.15	$111.20
Purchase #7	$244.48	7.258%	$262.2244	$262.22	$262.20	$262.20
7 purchase totals =	$1,005.52		$1,100.8906	$1,100.89	$1,100.85	$1,100.90