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	$223.44	6.524%	$238.0172	$238.02	$238.00	$238.00
Purchase #2	$99.72	4.199%	$103.9072	$103.91	$103.90	$103.90
Purchase #3	$17.72	4.801%	$18.5707	$18.57	$18.55	$18.60
Purchase #4	$183.68	4.681%	$192.2781	$192.28	$192.30	$192.30
Purchase #5	$250.91	6.653%	$267.603	$267.60	$267.60	$267.60
Purchase #6	$164.89	7.119%	$176.6285	$176.63	$176.65	$176.60
Purchase #7	$56.54	12.788%	$63.7703	$63.77	$63.75	$63.80
7 purchase totals =	$996.90		$1,060.7750	$1,060.78	$1,060.75	$1,060.80