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	$172.88	9.331%	$189.0114	$189.01	$189.00	$189.00
Purchase #2	$174.82	12.396%	$196.4907	$196.49	$196.50	$196.50
Purchase #3	$186.43	9.610%	$204.3459	$204.35	$204.35	$204.30
Purchase #4	$142.97	6.299%	$151.9757	$151.98	$152.00	$152.00
Purchase #5	$185.59	6.604%	$197.8464	$197.85	$197.85	$197.80
Purchase #6	$70.84	10.626%	$78.3675	$78.37	$78.35	$78.40
Purchase #7	$75.39	13.780%	$85.7787	$85.78	$85.80	$85.80
7 purchase totals =	$1,008.92		$1,103.8163	$1,103.83	$1,103.85	$1,103.80