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	$103.32	10.397%	$114.0622	$114.06	$114.05	$114.10
Purchase #2	$238.90	11.657%	$266.7486	$266.75	$266.75	$266.70
Purchase #3	$85.99	5.681%	$90.8751	$90.88	$90.90	$90.90
Purchase #4	$134.72	11.857%	$150.6938	$150.69	$150.70	$150.70
Purchase #5	$64.36	11.113%	$71.5123	$71.51	$71.50	$71.50
Purchase #6	$34.78	11.220%	$38.6823	$38.68	$38.70	$38.70
Purchase #7	$45.39	8.699%	$49.3385	$49.34	$49.35	$49.30
7 purchase totals =	$707.46		$781.9128	$781.91	$781.95	$781.90