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	$92.43	4.178%	$96.2917	$96.29	$96.30	$96.30
Purchase #2	$69.59	4.511%	$72.7292	$72.73	$72.75	$72.70
Purchase #3	$39.44	8.257%	$42.6966	$42.70	$42.70	$42.70
Purchase #4	$87.86	9.735%	$96.4132	$96.41	$96.40	$96.40
Purchase #5	$200.25	11.263%	$222.8042	$222.80	$222.80	$222.80
Purchase #6	$40.25	8.195%	$43.5485	$43.55	$43.55	$43.50
Purchase #7	$30.46	8.672%	$33.1015	$33.10	$33.10	$33.10
7 purchase totals =	$560.28		$607.5849	$607.58	$607.60	$607.50