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	$62.66	11.477%	$69.8515	$69.85	$69.85	$69.90
Purchase #2	$130.44	5.537%	$137.6625	$137.66	$137.65	$137.70
Purchase #3	$235.31	8.314%	$254.8737	$254.87	$254.85	$254.90
Purchase #4	$196.33	4.809%	$205.7715	$205.77	$205.75	$205.80
Purchase #5	$157.26	10.542%	$173.8383	$173.84	$173.85	$173.80
Purchase #6	$174.33	7.467%	$187.3472	$187.35	$187.35	$187.30
Purchase #7	$126.46	3.718%	$131.1618	$131.16	$131.15	$131.20
7 purchase totals =	$1,082.79		$1,160.5065	$1,160.50	$1,160.45	$1,160.60