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	$200.27	4.785%	$209.8529	$209.85	$209.85	$209.90
Purchase #2	$224.37	13.347%	$254.3167	$254.32	$254.30	$254.30
Purchase #3	$112.92	12.834%	$127.4122	$127.41	$127.40	$127.40
Purchase #4	$88.74	4.856%	$93.0492	$93.05	$93.05	$93.00
Purchase #5	$119.94	11.484%	$133.7139	$133.71	$133.70	$133.70
Purchase #6	$103.48	7.550%	$111.2927	$111.29	$111.30	$111.30
Purchase #7	$75.25	6.521%	$80.1571	$80.16	$80.15	$80.20
7 purchase totals =	$924.97		$1,009.7947	$1,009.79	$1,009.75	$1,009.80