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	$213.56	10.725%	$236.4643	$236.46	$236.45	$236.50
Purchase #2	$180.54	9.752%	$198.1463	$198.15	$198.15	$198.10
Purchase #3	$131.51	4.697%	$137.687	$137.69	$137.70	$137.70
Purchase #4	$211.25	10.743%	$233.9446	$233.94	$233.95	$233.90
Purchase #5	$78.40	13.378%	$88.8884	$88.89	$88.90	$88.90
Purchase #6	$74.50	4.731%	$78.0246	$78.02	$78.00	$78.00
Purchase #7	$25.99	9.444%	$28.4445	$28.44	$28.45	$28.40
7 purchase totals =	$915.75		$1,001.5997	$1,001.59	$1,001.60	$1,001.50