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	$145.88	6.417%	$155.2411	$155.24	$155.25	$155.20
Purchase #2	$111.70	10.423%	$123.3425	$123.34	$123.35	$123.30
Purchase #3	$52.62	6.645%	$56.1166	$56.12	$56.10	$56.10
Purchase #4	$37.67	7.829%	$40.6192	$40.62	$40.60	$40.60
Purchase #5	$235.72	3.797%	$244.6703	$244.67	$244.65	$244.70
Purchase #6	$125.30	5.238%	$131.8632	$131.86	$131.85	$131.90
Purchase #7	$157.66	5.740%	$166.7097	$166.71	$166.70	$166.70
7 purchase totals =	$866.55		$918.5626	$918.56	$918.50	$918.50