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	$204.47	6.577%	$217.918	$217.92	$217.90	$217.90
Purchase #2	$187.28	3.253%	$193.3722	$193.37	$193.35	$193.40
Purchase #3	$183.69	4.164%	$191.3389	$191.34	$191.35	$191.30
Purchase #4	$18.32	3.364%	$18.9363	$18.94	$18.95	$18.90
Purchase #5	$84.56	7.513%	$90.913	$90.91	$90.90	$90.90
Purchase #6	$58.54	5.811%	$61.9418	$61.94	$61.95	$61.90
Purchase #7	$26.93	6.192%	$28.5975	$28.60	$28.60	$28.60
7 purchase totals =	$763.79		$803.0177	$803.02	$803.00	$802.90