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	$175.66	11.810%	$196.4054	$196.41	$196.40	$196.40
Purchase #2	$240.40	3.765%	$249.4511	$249.45	$249.45	$249.50
Purchase #3	$11.51	10.843%	$12.758	$12.76	$12.75	$12.80
Purchase #4	$169.47	9.796%	$186.0713	$186.07	$186.05	$186.10
Purchase #5	$242.95	9.358%	$265.6853	$265.69	$265.70	$265.70
Purchase #6	$240.94	6.608%	$256.8613	$256.86	$256.85	$256.90
Purchase #7	$51.53	6.507%	$54.8831	$54.88	$54.90	$54.90
7 purchase totals =	$1,132.46		$1,222.1155	$1,222.12	$1,222.10	$1,222.30