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	$122.25	7.654%	$131.607	$131.61	$131.60	$131.60
Purchase #2	$44.89	6.251%	$47.6961	$47.70	$47.70	$47.70
Purchase #3	$185.60	6.122%	$196.9624	$196.96	$196.95	$197.00
Purchase #4	$70.67	11.470%	$78.7758	$78.78	$78.80	$78.80
Purchase #5	$98.51	7.161%	$105.5643	$105.56	$105.55	$105.60
Purchase #6	$7.36	7.581%	$7.918	$7.92	$7.90	$7.90
Purchase #7	$223.68	6.370%	$237.9284	$237.93	$237.95	$237.90
7 purchase totals =	$752.96		$806.4520	$806.46	$806.45	$806.50