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	$160.91	10.136%	$177.2198	$177.22	$177.20	$177.20
Purchase #2	$181.73	6.167%	$192.9373	$192.94	$192.95	$192.90
Purchase #3	$81.65	5.304%	$85.9807	$85.98	$86.00	$86.00
Purchase #4	$133.38	8.650%	$144.9174	$144.92	$144.90	$144.90
Purchase #5	$71.61	10.194%	$78.9099	$78.91	$78.90	$78.90
Purchase #6	$105.84	10.681%	$117.1448	$117.14	$117.15	$117.10
Purchase #7	$197.32	12.415%	$221.8173	$221.82	$221.80	$221.80
7 purchase totals =	$932.44		$1,018.9272	$1,018.93	$1,018.90	$1,018.80