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	$55.78	8.654%	$60.6072	$60.61	$60.60	$60.60
Purchase #2	$248.88	7.337%	$267.1403	$267.14	$267.15	$267.10
Purchase #3	$119.95	13.794%	$136.4959	$136.50	$136.50	$136.50
Purchase #4	$246.33	13.155%	$278.7347	$278.73	$278.75	$278.70
Purchase #5	$36.65	11.144%	$40.7343	$40.73	$40.75	$40.70
Purchase #6	$178.51	10.192%	$196.7037	$196.70	$196.70	$196.70
Purchase #7	$75.85	13.348%	$85.9745	$85.97	$85.95	$86.00
7 purchase totals =	$961.95		$1,066.3906	$1,066.38	$1,066.40	$1,066.30