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	$158.55	9.184%	$173.1112	$173.11	$173.10	$173.10
Purchase #2	$67.45	6.166%	$71.609	$71.61	$71.60	$71.60
Purchase #3	$81.65	10.589%	$90.2959	$90.30	$90.30	$90.30
Purchase #4	$163.83	12.821%	$184.8346	$184.83	$184.85	$184.80
Purchase #5	$36.94	4.846%	$38.7301	$38.73	$38.75	$38.70
Purchase #6	$248.70	8.589%	$270.0608	$270.06	$270.05	$270.10
Purchase #7	$168.58	12.197%	$189.1417	$189.14	$189.15	$189.10
7 purchase totals =	$925.70		$1,017.7833	$1,017.78	$1,017.80	$1,017.70