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	$211.44	8.484%	$229.3786	$229.38	$229.40	$229.40
Purchase #2	$28.30	11.138%	$31.4521	$31.45	$31.45	$31.50
Purchase #3	$205.52	13.620%	$233.5118	$233.51	$233.50	$233.50
Purchase #4	$167.87	6.295%	$178.4374	$178.44	$178.45	$178.40
Purchase #5	$203.98	7.543%	$219.3662	$219.37	$219.35	$219.40
Purchase #6	$127.28	13.280%	$144.1828	$144.18	$144.20	$144.20
Purchase #7	$9.38	8.541%	$10.1811	$10.18	$10.20	$10.20
7 purchase totals =	$953.77		$1,046.5100	$1,046.51	$1,046.55	$1,046.60