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	$146.75	3.529%	$151.9288	$151.93	$151.95	$151.90
Purchase #2	$175.45	11.714%	$196.0022	$196.00	$196.00	$196.00
Purchase #3	$72.71	8.600%	$78.9631	$78.96	$78.95	$79.00
Purchase #4	$133.76	7.186%	$143.372	$143.37	$143.35	$143.40
Purchase #5	$110.85	7.618%	$119.2946	$119.29	$119.30	$119.30
Purchase #6	$250.96	4.718%	$262.8003	$262.80	$262.80	$262.80
Purchase #7	$58.76	3.660%	$60.9106	$60.91	$60.90	$60.90
7 purchase totals =	$949.24		$1,013.2716	$1,013.26	$1,013.25	$1,013.30