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	$139.61	5.394%	$147.1406	$147.14	$147.15	$147.10
Purchase #2	$20.57	11.176%	$22.8689	$22.87	$22.85	$22.90
Purchase #3	$135.29	5.365%	$142.5483	$142.55	$142.55	$142.50
Purchase #4	$73.77	3.471%	$76.3306	$76.33	$76.35	$76.30
Purchase #5	$9.86	6.751%	$10.5256	$10.53	$10.55	$10.50
Purchase #6	$182.90	7.281%	$196.2169	$196.22	$196.20	$196.20
Purchase #7	$120.55	6.770%	$128.7112	$128.71	$128.70	$128.70
7 purchase totals =	$682.55		$724.3421	$724.35	$724.35	$724.20