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	$92.68	6.565%	$98.7644	$98.76	$98.75	$98.80
Purchase #2	$236.48	5.562%	$249.633	$249.63	$249.65	$249.60
Purchase #3	$63.42	6.240%	$67.3774	$67.38	$67.40	$67.40
Purchase #4	$214.67	7.119%	$229.9524	$229.95	$229.95	$230.00
Purchase #5	$69.74	4.542%	$72.9076	$72.91	$72.90	$72.90
Purchase #6	$69.94	12.164%	$78.4475	$78.45	$78.45	$78.40
Purchase #7	$247.96	11.521%	$276.5275	$276.53	$276.55	$276.50
7 purchase totals =	$994.89		$1,073.6098	$1,073.61	$1,073.65	$1,073.60