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	$96.68	8.787%	$105.1753	$105.18	$105.20	$105.20
Purchase #2	$240.62	11.312%	$267.8389	$267.84	$267.85	$267.80
Purchase #3	$80.26	7.542%	$86.3132	$86.31	$86.30	$86.30
Purchase #4	$158.77	7.815%	$171.1779	$171.18	$171.20	$171.20
Purchase #5	$154.32	11.386%	$171.8909	$171.89	$171.90	$171.90
Purchase #6	$200.37	10.238%	$220.8839	$220.88	$220.90	$220.90
Purchase #7	$130.36	9.218%	$142.3766	$142.38	$142.40	$142.40
7 purchase totals =	$1,061.38		$1,165.6567	$1,165.66	$1,165.75	$1,165.70