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	$119.62	6.217%	$127.0568	$127.06	$127.05	$127.10
Purchase #2	$98.25	4.218%	$102.3942	$102.39	$102.40	$102.40
Purchase #3	$62.28	6.459%	$66.3027	$66.30	$66.30	$66.30
Purchase #4	$204.65	5.533%	$215.9733	$215.97	$215.95	$216.00
Purchase #5	$105.66	13.627%	$120.0583	$120.06	$120.05	$120.10
Purchase #6	$102.47	6.775%	$109.4123	$109.41	$109.40	$109.40
Purchase #7	$28.97	12.207%	$32.5064	$32.51	$32.50	$32.50
7 purchase totals =	$721.90		$773.7040	$773.70	$773.65	$773.80