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	$82.80	3.816%	$85.9596	$85.96	$85.95	$86.00
Purchase #2	$229.30	13.572%	$260.4206	$260.42	$260.40	$260.40
Purchase #3	$125.72	13.483%	$142.6708	$142.67	$142.65	$142.70
Purchase #4	$174.54	11.690%	$194.9437	$194.94	$194.95	$194.90
Purchase #5	$11.28	11.616%	$12.5903	$12.59	$12.60	$12.60
Purchase #6	$33.51	11.475%	$37.3553	$37.36	$37.35	$37.40
Purchase #7	$30.90	3.512%	$31.9852	$31.99	$32.00	$32.00
7 purchase totals =	$688.05		$765.9255	$765.93	$765.90	$766.00