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	$63.86	8.292%	$69.1553	$69.16	$69.15	$69.20
Purchase #2	$27.67	12.628%	$31.1642	$31.16	$31.15	$31.20
Purchase #3	$63.39	12.745%	$71.4691	$71.47	$71.45	$71.50
Purchase #4	$190.56	3.122%	$196.5093	$196.51	$196.50	$196.50
Purchase #5	$46.36	4.419%	$48.4086	$48.41	$48.40	$48.40
Purchase #6	$100.43	6.348%	$106.8053	$106.81	$106.80	$106.80
Purchase #7	$83.59	13.276%	$94.6874	$94.69	$94.70	$94.70
7 purchase totals =	$575.86		$618.1992	$618.21	$618.15	$618.30