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	$231.64	6.185%	$245.9669	$245.97	$245.95	$246.00
Purchase #2	$69.34	3.700%	$71.9056	$71.91	$71.90	$71.90
Purchase #3	$127.55	3.135%	$131.5487	$131.55	$131.55	$131.50
Purchase #4	$145.75	8.779%	$158.5454	$158.55	$158.55	$158.50
Purchase #5	$150.54	6.273%	$159.9834	$159.98	$160.00	$160.00
Purchase #6	$18.50	10.600%	$20.461	$20.46	$20.45	$20.50
Purchase #7	$202.97	8.592%	$220.4092	$220.41	$220.40	$220.40
7 purchase totals =	$946.29		$1,008.8202	$1,008.83	$1,008.80	$1,008.80