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	$144.44	5.424%	$152.2744	$152.27	$152.25	$152.30
Purchase #2	$175.31	6.271%	$186.3037	$186.30	$186.30	$186.30
Purchase #3	$176.87	13.346%	$200.4751	$200.48	$200.50	$200.50
Purchase #4	$109.78	13.641%	$124.7551	$124.76	$124.75	$124.80
Purchase #5	$171.99	10.697%	$190.3878	$190.39	$190.40	$190.40
Purchase #6	$84.76	4.855%	$88.8751	$88.88	$88.90	$88.90
Purchase #7	$183.87	13.527%	$208.7421	$208.74	$208.75	$208.70
7 purchase totals =	$1,047.02		$1,151.8133	$1,151.82	$1,151.85	$1,151.90