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	$86.36	4.131%	$89.9275	$89.93	$89.95	$89.90
Purchase #2	$83.79	3.430%	$86.664	$86.66	$86.65	$86.70
Purchase #3	$229.72	7.759%	$247.544	$247.54	$247.55	$247.50
Purchase #4	$95.87	12.180%	$107.547	$107.55	$107.55	$107.50
Purchase #5	$222.92	12.186%	$250.085	$250.09	$250.10	$250.10
Purchase #6	$159.44	5.816%	$168.713	$168.71	$168.70	$168.70
Purchase #7	$103.39	5.870%	$109.459	$109.46	$109.45	$109.50
7 purchase totals =	$981.49		$1,059.9395	$1,059.94	$1,059.95	$1,059.90