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	$186.49	7.415%	$200.3182	$200.32	$200.30	$200.30
Purchase #2	$124.63	4.816%	$130.6322	$130.63	$130.65	$130.60
Purchase #3	$69.76	3.307%	$72.067	$72.07	$72.05	$72.10
Purchase #4	$209.93	4.858%	$220.1284	$220.13	$220.15	$220.10
Purchase #5	$231.75	4.582%	$242.3688	$242.37	$242.35	$242.40
Purchase #6	$43.37	6.651%	$46.2545	$46.25	$46.25	$46.30
Purchase #7	$81.30	10.843%	$90.1154	$90.12	$90.10	$90.10
7 purchase totals =	$947.23		$1,001.8845	$1,001.89	$1,001.85	$1,001.90