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	$76.55	7.418%	$82.2285	$82.23	$82.25	$82.20
Purchase #2	$206.94	12.155%	$232.0936	$232.09	$232.10	$232.10
Purchase #3	$121.92	4.214%	$127.0577	$127.06	$127.05	$127.10
Purchase #4	$51.34	4.793%	$53.8007	$53.80	$53.80	$53.80
Purchase #5	$199.58	3.550%	$206.6651	$206.67	$206.65	$206.70
Purchase #6	$93.91	6.253%	$99.7822	$99.78	$99.80	$99.80
Purchase #7	$119.93	6.588%	$127.831	$127.83	$127.85	$127.80
7 purchase totals =	$870.17		$929.4588	$929.46	$929.50	$929.50