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	$208.73	6.409%	$222.1075	$222.11	$222.10	$222.10
Purchase #2	$182.46	4.622%	$190.8933	$190.89	$190.90	$190.90
Purchase #3	$63.64	8.520%	$69.0621	$69.06	$69.05	$69.10
Purchase #4	$244.98	8.132%	$264.9018	$264.90	$264.90	$264.90
Purchase #5	$74.66	5.212%	$78.5513	$78.55	$78.55	$78.60
Purchase #6	$194.46	4.162%	$202.5534	$202.55	$202.55	$202.60
Purchase #7	$140.91	3.243%	$145.4797	$145.48	$145.50	$145.50
7 purchase totals =	$1,109.84		$1,173.5491	$1,173.54	$1,173.55	$1,173.70