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	$153.37	9.706%	$168.2561	$168.26	$168.25	$168.30
Purchase #2	$55.95	12.410%	$62.8934	$62.89	$62.90	$62.90
Purchase #3	$168.61	13.269%	$190.9829	$190.98	$191.00	$191.00
Purchase #4	$39.71	4.545%	$41.5148	$41.51	$41.50	$41.50
Purchase #5	$172.79	12.307%	$194.0553	$194.06	$194.05	$194.10
Purchase #6	$205.76	8.435%	$223.1159	$223.12	$223.10	$223.10
Purchase #7	$141.53	9.258%	$154.6328	$154.63	$154.65	$154.60
7 purchase totals =	$937.72		$1,035.4512	$1,035.45	$1,035.45	$1,035.50