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	$245.80	3.796%	$255.1306	$255.13	$255.15	$255.10
Purchase #2	$140.30	4.859%	$147.1172	$147.12	$147.10	$147.10
Purchase #3	$149.51	6.378%	$159.0457	$159.05	$159.05	$159.00
Purchase #4	$182.27	7.816%	$196.5162	$196.52	$196.50	$196.50
Purchase #5	$98.97	10.389%	$109.252	$109.25	$109.25	$109.30
Purchase #6	$65.29	9.756%	$71.6597	$71.66	$71.65	$71.70
Purchase #7	$224.86	9.481%	$246.179	$246.18	$246.20	$246.20
7 purchase totals =	$1,107.00		$1,184.9004	$1,184.91	$1,184.90	$1,184.90