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	$109.76	11.627%	$122.5218	$122.52	$122.50	$122.50
Purchase #2	$225.29	4.707%	$235.8944	$235.89	$235.90	$235.90
Purchase #3	$82.27	4.510%	$85.9804	$85.98	$86.00	$86.00
Purchase #4	$180.45	9.123%	$196.9125	$196.91	$196.90	$196.90
Purchase #5	$83.28	8.194%	$90.104	$90.10	$90.10	$90.10
Purchase #6	$189.77	8.520%	$205.9384	$205.94	$205.95	$205.90
Purchase #7	$189.98	8.853%	$206.7989	$206.80	$206.80	$206.80
7 purchase totals =	$1,060.80		$1,144.1504	$1,144.14	$1,144.15	$1,144.10