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	$167.57	10.490%	$185.1481	$185.15	$185.15	$185.10
Purchase #2	$44.54	6.732%	$47.5384	$47.54	$47.55	$47.50
Purchase #3	$117.94	7.751%	$127.0815	$127.08	$127.10	$127.10
Purchase #4	$163.96	9.382%	$179.3427	$179.34	$179.35	$179.30
Purchase #5	$238.35	12.374%	$267.8434	$267.84	$267.85	$267.80
Purchase #6	$57.40	8.111%	$62.0557	$62.06	$62.05	$62.10
Purchase #7	$143.36	6.102%	$152.1078	$152.11	$152.10	$152.10
7 purchase totals =	$933.12		$1,021.1176	$1,021.12	$1,021.15	$1,021.00