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	$78.74	10.596%	$87.0833	$87.08	$87.10	$87.10
Purchase #2	$227.90	11.454%	$254.0037	$254.00	$254.00	$254.00
Purchase #3	$185.98	7.328%	$199.6086	$199.61	$199.60	$199.60
Purchase #4	$177.94	10.345%	$196.3479	$196.35	$196.35	$196.30
Purchase #5	$147.82	10.632%	$163.5362	$163.54	$163.55	$163.50
Purchase #6	$150.68	11.159%	$167.4944	$167.49	$167.50	$167.50
Purchase #7	$115.53	7.148%	$123.7881	$123.79	$123.80	$123.80
7 purchase totals =	$1,084.59		$1,191.8622	$1,191.86	$1,191.90	$1,191.80