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	$49.71	4.414%	$51.9042	$51.90	$51.90	$51.90
Purchase #2	$237.95	12.581%	$267.8865	$267.89	$267.90	$267.90
Purchase #3	$72.41	7.793%	$78.0529	$78.05	$78.05	$78.10
Purchase #4	$232.29	4.633%	$243.052	$243.05	$243.05	$243.10
Purchase #5	$250.70	4.455%	$261.8687	$261.87	$261.85	$261.90
Purchase #6	$139.78	9.241%	$152.6971	$152.70	$152.70	$152.70
Purchase #7	$179.43	9.342%	$196.1924	$196.19	$196.20	$196.20
7 purchase totals =	$1,162.27		$1,251.6538	$1,251.65	$1,251.65	$1,251.80