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	$85.53	10.393%	$94.4191	$94.42	$94.40	$94.40
Purchase #2	$166.39	7.672%	$179.1554	$179.16	$179.15	$179.20
Purchase #3	$206.41	7.334%	$221.5481	$221.55	$221.55	$221.50
Purchase #4	$192.28	3.355%	$198.731	$198.73	$198.75	$198.70
Purchase #5	$114.95	10.491%	$127.0094	$127.01	$127.00	$127.00
Purchase #6	$150.40	11.601%	$167.8479	$167.85	$167.85	$167.80
Purchase #7	$164.78	5.753%	$174.2598	$174.26	$174.25	$174.30
7 purchase totals =	$1,080.74		$1,162.9707	$1,162.98	$1,162.95	$1,162.90