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	$162.56	5.737%	$171.8861	$171.89	$171.90	$171.90
Purchase #2	$154.63	5.553%	$163.2166	$163.22	$163.20	$163.20
Purchase #3	$79.76	7.132%	$85.4485	$85.45	$85.45	$85.40
Purchase #4	$228.49	9.359%	$249.8744	$249.87	$249.85	$249.90
Purchase #5	$42.93	6.710%	$45.8106	$45.81	$45.80	$45.80
Purchase #6	$157.43	3.146%	$162.3827	$162.38	$162.40	$162.40
Purchase #7	$120.51	13.809%	$137.1512	$137.15	$137.15	$137.20
7 purchase totals =	$946.31		$1,015.7701	$1,015.77	$1,015.75	$1,015.80