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	$56.79	4.323%	$59.245	$59.25	$59.25	$59.20
Purchase #2	$234.95	8.291%	$254.4297	$254.43	$254.45	$254.40
Purchase #3	$237.63	6.843%	$253.891	$253.89	$253.90	$253.90
Purchase #4	$31.86	5.267%	$33.5381	$33.54	$33.55	$33.50
Purchase #5	$88.77	8.451%	$96.272	$96.27	$96.25	$96.30
Purchase #6	$228.91	9.565%	$250.8052	$250.81	$250.80	$250.80
Purchase #7	$55.42	11.833%	$61.9778	$61.98	$62.00	$62.00
7 purchase totals =	$934.33		$1,010.1588	$1,010.17	$1,010.20	$1,010.10