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	$150.35	3.194%	$155.1522	$155.15	$155.15	$155.20
Purchase #2	$34.28	7.569%	$36.8747	$36.87	$36.85	$36.90
Purchase #3	$120.53	9.443%	$131.9116	$131.91	$131.90	$131.90
Purchase #4	$19.87	9.808%	$21.8188	$21.82	$21.80	$21.80
Purchase #5	$203.34	4.377%	$212.2402	$212.24	$212.25	$212.20
Purchase #6	$225.71	6.704%	$240.8416	$240.84	$240.85	$240.80
Purchase #7	$91.82	5.510%	$96.8793	$96.88	$96.90	$96.90
7 purchase totals =	$845.90		$895.7184	$895.71	$895.70	$895.70