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	$53.82	12.151%	$60.3597	$60.36	$60.35	$60.40
Purchase #2	$105.88	3.325%	$109.4005	$109.40	$109.40	$109.40
Purchase #3	$67.42	7.597%	$72.5419	$72.54	$72.55	$72.50
Purchase #4	$27.66	3.805%	$28.7125	$28.71	$28.70	$28.70
Purchase #5	$47.86	7.816%	$51.6007	$51.60	$51.60	$51.60
Purchase #6	$121.73	8.488%	$132.0624	$132.06	$132.05	$132.10
Purchase #7	$174.72	13.697%	$198.6514	$198.65	$198.65	$198.70
7 purchase totals =	$599.09		$653.3291	$653.32	$653.30	$653.40