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	$161.94	4.112%	$168.599	$168.60	$168.60	$168.60
Purchase #2	$152.97	4.227%	$159.436	$159.44	$159.45	$159.40
Purchase #3	$205.55	3.226%	$212.181	$212.18	$212.20	$212.20
Purchase #4	$136.41	13.134%	$154.3261	$154.33	$154.35	$154.30
Purchase #5	$112.43	12.163%	$126.1049	$126.10	$126.10	$126.10
Purchase #6	$96.41	4.627%	$100.8709	$100.87	$100.85	$100.90
Purchase #7	$137.31	12.244%	$154.1222	$154.12	$154.10	$154.10
7 purchase totals =	$1,003.02		$1,075.6401	$1,075.64	$1,075.65	$1,075.60