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	$134.90	9.232%	$147.354	$147.35	$147.35	$147.40
Purchase #2	$50.39	4.747%	$52.782	$52.78	$52.80	$52.80
Purchase #3	$165.85	5.769%	$175.4179	$175.42	$175.40	$175.40
Purchase #4	$145.71	9.531%	$159.5976	$159.60	$159.60	$159.60
Purchase #5	$97.69	12.459%	$109.8612	$109.86	$109.85	$109.90
Purchase #6	$92.78	6.208%	$98.5398	$98.54	$98.55	$98.50
Purchase #7	$103.72	3.750%	$107.6095	$107.61	$107.60	$107.60
7 purchase totals =	$791.04		$851.1620	$851.16	$851.15	$851.20