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	$83.87	5.721%	$88.6682	$88.67	$88.65	$88.70
Purchase #2	$84.47	4.195%	$88.0135	$88.01	$88.00	$88.00
Purchase #3	$117.72	5.180%	$123.8179	$123.82	$123.80	$123.80
Purchase #4	$236.29	6.377%	$251.3582	$251.36	$251.35	$251.40
Purchase #5	$133.29	13.465%	$151.2375	$151.24	$151.25	$151.20
Purchase #6	$167.30	9.238%	$182.7552	$182.76	$182.75	$182.80
Purchase #7	$45.64	4.262%	$47.5852	$47.59	$47.60	$47.60
7 purchase totals =	$868.58		$933.4357	$933.45	$933.40	$933.50