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	$53.89	10.345%	$59.4649	$59.46	$59.45	$59.50
Purchase #2	$94.99	13.755%	$108.0559	$108.06	$108.05	$108.10
Purchase #3	$204.98	11.529%	$228.6121	$228.61	$228.60	$228.60
Purchase #4	$109.40	7.866%	$118.0054	$118.01	$118.00	$118.00
Purchase #5	$115.46	7.185%	$123.7558	$123.76	$123.75	$123.80
Purchase #6	$207.31	8.354%	$224.6287	$224.63	$224.65	$224.60
Purchase #7	$160.48	10.851%	$177.8937	$177.89	$177.90	$177.90
7 purchase totals =	$946.51		$1,040.4165	$1,040.42	$1,040.40	$1,040.50