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	$64.64	9.290%	$70.6451	$70.65	$70.65	$70.60
Purchase #2	$131.67	7.479%	$141.5176	$141.52	$141.50	$141.50
Purchase #3	$141.79	9.764%	$155.6344	$155.63	$155.65	$155.60
Purchase #4	$218.67	8.855%	$238.0332	$238.03	$238.05	$238.00
Purchase #5	$199.58	10.308%	$220.1527	$220.15	$220.15	$220.20
Purchase #6	$86.94	11.561%	$96.9911	$96.99	$97.00	$97.00
Purchase #7	$82.62	8.804%	$89.8939	$89.89	$89.90	$89.90
7 purchase totals =	$925.91		$1,012.8680	$1,012.86	$1,012.90	$1,012.80