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	$78.71	4.593%	$82.3252	$82.33	$82.35	$82.30
Purchase #2	$236.71	6.287%	$251.592	$251.59	$251.60	$251.60
Purchase #3	$118.27	10.605%	$130.8125	$130.81	$130.80	$130.80
Purchase #4	$58.52	9.363%	$63.9992	$64.00	$64.00	$64.00
Purchase #5	$198.98	6.316%	$211.5476	$211.55	$211.55	$211.50
Purchase #6	$215.49	12.608%	$242.659	$242.66	$242.65	$242.70
Purchase #7	$104.60	7.391%	$112.331	$112.33	$112.35	$112.30
7 purchase totals =	$1,011.28		$1,095.2665	$1,095.27	$1,095.30	$1,095.20