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	$106.31	3.340%	$109.8608	$109.86	$109.85	$109.90
Purchase #2	$235.83	6.546%	$251.2674	$251.27	$251.25	$251.30
Purchase #3	$71.75	4.822%	$75.2098	$75.21	$75.20	$75.20
Purchase #4	$142.93	9.353%	$156.2982	$156.30	$156.30	$156.30
Purchase #5	$231.54	10.422%	$255.6711	$255.67	$255.65	$255.70
Purchase #6	$180.26	7.772%	$194.2698	$194.27	$194.25	$194.30
Purchase #7	$78.59	13.240%	$88.9953	$89.00	$89.00	$89.00
7 purchase totals =	$1,047.21		$1,131.5724	$1,131.58	$1,131.50	$1,131.70