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	$94.96	9.405%	$103.891	$103.89	$103.90	$103.90
Purchase #2	$46.78	13.250%	$52.9784	$52.98	$53.00	$53.00
Purchase #3	$127.33	6.354%	$135.4205	$135.42	$135.40	$135.40
Purchase #4	$249.33	13.320%	$282.5408	$282.54	$282.55	$282.50
Purchase #5	$216.27	8.105%	$233.7987	$233.80	$233.80	$233.80
Purchase #6	$203.38	12.134%	$228.0581	$228.06	$228.05	$228.10
Purchase #7	$37.42	8.356%	$40.5468	$40.55	$40.55	$40.50
7 purchase totals =	$975.47		$1,077.2343	$1,077.24	$1,077.25	$1,077.20