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	$82.26	11.165%	$91.4443	$91.44	$91.45	$91.40
Purchase #2	$248.45	11.344%	$276.6342	$276.63	$276.65	$276.60
Purchase #3	$120.88	7.354%	$129.7695	$129.77	$129.75	$129.80
Purchase #4	$86.89	4.839%	$91.0946	$91.09	$91.10	$91.10
Purchase #5	$54.26	4.151%	$56.5123	$56.51	$56.50	$56.50
Purchase #6	$161.79	12.869%	$182.6108	$182.61	$182.60	$182.60
Purchase #7	$221.32	5.404%	$233.2801	$233.28	$233.30	$233.30
7 purchase totals =	$975.85		$1,061.3458	$1,061.33	$1,061.35	$1,061.30