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	$47.74	10.278%	$52.6467	$52.65	$52.65	$52.60
Purchase #2	$51.97	10.795%	$57.5802	$57.58	$57.60	$57.60
Purchase #3	$228.58	13.144%	$258.6246	$258.62	$258.60	$258.60
Purchase #4	$246.71	9.492%	$270.1277	$270.13	$270.15	$270.10
Purchase #5	$196.51	13.705%	$223.4417	$223.44	$223.45	$223.40
Purchase #6	$160.97	11.660%	$179.7391	$179.74	$179.75	$179.70
Purchase #7	$154.41	9.139%	$168.5215	$168.52	$168.50	$168.50
7 purchase totals =	$1,086.89		$1,210.6815	$1,210.68	$1,210.70	$1,210.50