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	$191.64	6.418%	$203.9395	$203.94	$203.95	$203.90
Purchase #2	$38.54	13.325%	$43.6755	$43.68	$43.70	$43.70
Purchase #3	$103.70	9.841%	$113.9051	$113.91	$113.90	$113.90
Purchase #4	$24.91	13.476%	$28.2669	$28.27	$28.25	$28.30
Purchase #5	$71.37	9.787%	$78.355	$78.36	$78.35	$78.40
Purchase #6	$56.86	13.661%	$64.6276	$64.63	$64.65	$64.60
Purchase #7	$168.48	13.427%	$191.1018	$191.10	$191.10	$191.10
7 purchase totals =	$655.50		$723.8714	$723.89	$723.90	$723.90