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	$147.73	7.853%	$159.3312	$159.33	$159.35	$159.30
Purchase #2	$33.98	10.258%	$37.4657	$37.47	$37.45	$37.50
Purchase #3	$186.86	4.641%	$195.5322	$195.53	$195.55	$195.50
Purchase #4	$180.32	3.192%	$186.0758	$186.08	$186.10	$186.10
Purchase #5	$53.25	3.212%	$54.9604	$54.96	$54.95	$55.00
Purchase #6	$64.67	10.252%	$71.3	$71.30	$71.30	$71.30
Purchase #7	$193.64	6.139%	$205.5276	$205.53	$205.55	$205.50
7 purchase totals =	$860.45		$910.1929	$910.20	$910.25	$910.20