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	$187.73	4.512%	$196.2004	$196.20	$196.20	$196.20
Purchase #2	$20.75	10.562%	$22.9416	$22.94	$22.95	$22.90
Purchase #3	$177.54	10.137%	$195.5372	$195.54	$195.55	$195.50
Purchase #4	$12.49	6.652%	$13.3208	$13.32	$13.30	$13.30
Purchase #5	$209.60	11.425%	$233.5468	$233.55	$233.55	$233.50
Purchase #6	$159.49	3.381%	$164.8824	$164.88	$164.90	$164.90
Purchase #7	$60.83	6.683%	$64.8953	$64.90	$64.90	$64.90
7 purchase totals =	$828.43		$891.3245	$891.33	$891.35	$891.20