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	$57.51	7.721%	$61.9503	$61.95	$61.95	$62.00
Purchase #2	$21.30	13.774%	$24.2339	$24.23	$24.25	$24.20
Purchase #3	$89.54	6.648%	$95.4926	$95.49	$95.50	$95.50
Purchase #4	$99.31	12.751%	$111.973	$111.97	$111.95	$112.00
Purchase #5	$71.97	10.606%	$79.6031	$79.60	$79.60	$79.60
Purchase #6	$18.38	12.185%	$20.6196	$20.62	$20.60	$20.60
Purchase #7	$32.73	3.436%	$33.8546	$33.85	$33.85	$33.90
7 purchase totals =	$390.74		$427.7271	$427.71	$427.70	$427.80