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	$93.95	9.750%	$103.1101	$103.11	$103.10	$103.10
Purchase #2	$64.36	7.635%	$69.2739	$69.27	$69.25	$69.30
Purchase #3	$156.98	12.320%	$176.3199	$176.32	$176.30	$176.30
Purchase #4	$227.59	10.476%	$251.4323	$251.43	$251.45	$251.40
Purchase #5	$85.25	12.320%	$95.7528	$95.75	$95.75	$95.80
Purchase #6	$241.78	3.458%	$250.1408	$250.14	$250.15	$250.10
Purchase #7	$53.59	10.781%	$59.3675	$59.37	$59.35	$59.40
7 purchase totals =	$923.50		$1,005.3973	$1,005.39	$1,005.35	$1,005.40