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	$82.69	8.169%	$89.4449	$89.44	$89.45	$89.40
Purchase #2	$249.38	11.413%	$277.8417	$277.84	$277.85	$277.80
Purchase #3	$133.89	7.633%	$144.1098	$144.11	$144.10	$144.10
Purchase #4	$174.86	5.456%	$184.4004	$184.40	$184.40	$184.40
Purchase #5	$41.38	5.460%	$43.6393	$43.64	$43.65	$43.60
Purchase #6	$91.63	10.665%	$101.4023	$101.40	$101.40	$101.40
Purchase #7	$188.70	3.807%	$195.8838	$195.88	$195.90	$195.90
7 purchase totals =	$962.53		$1,036.7222	$1,036.71	$1,036.75	$1,036.60