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	$200.75	10.678%	$222.1861	$222.19	$222.20	$222.20
Purchase #2	$46.94	13.484%	$53.2694	$53.27	$53.25	$53.30
Purchase #3	$115.30	11.791%	$128.895	$128.90	$128.90	$128.90
Purchase #4	$26.71	11.251%	$29.7151	$29.72	$29.70	$29.70
Purchase #5	$78.26	10.118%	$86.1783	$86.18	$86.20	$86.20
Purchase #6	$84.68	6.372%	$90.0758	$90.08	$90.10	$90.10
Purchase #7	$168.86	5.867%	$178.767	$178.77	$178.75	$178.80
7 purchase totals =	$721.50		$789.0867	$789.11	$789.10	$789.20