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	$49.32	7.646%	$53.091	$53.09	$53.10	$53.10
Purchase #2	$68.88	3.631%	$71.381	$71.38	$71.40	$71.40
Purchase #3	$179.60	13.639%	$204.0956	$204.10	$204.10	$204.10
Purchase #4	$237.31	7.663%	$255.4951	$255.50	$255.50	$255.50
Purchase #5	$79.42	9.418%	$86.8998	$86.90	$86.90	$86.90
Purchase #6	$208.99	6.807%	$223.2159	$223.22	$223.20	$223.20
Purchase #7	$202.90	11.263%	$225.7526	$225.75	$225.75	$225.80
7 purchase totals =	$1,026.42		$1,119.9310	$1,119.94	$1,119.95	$1,120.00