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	$101.67	10.692%	$112.5406	$112.54	$112.55	$112.50
Purchase #2	$177.61	4.821%	$186.1726	$186.17	$186.15	$186.20
Purchase #3	$122.76	10.871%	$136.1052	$136.11	$136.10	$136.10
Purchase #4	$143.90	4.645%	$150.5842	$150.58	$150.60	$150.60
Purchase #5	$245.54	10.685%	$271.7759	$271.78	$271.80	$271.80
Purchase #6	$76.48	12.425%	$85.9826	$85.98	$86.00	$86.00
Purchase #7	$142.55	8.158%	$154.1792	$154.18	$154.20	$154.20
7 purchase totals =	$1,010.51		$1,097.3403	$1,097.34	$1,097.40	$1,097.40