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	$241.62	12.856%	$272.6827	$272.68	$272.70	$272.70
Purchase #2	$38.47	9.492%	$42.1216	$42.12	$42.10	$42.10
Purchase #3	$93.85	7.242%	$100.6466	$100.65	$100.65	$100.60
Purchase #4	$145.74	6.855%	$155.7305	$155.73	$155.75	$155.70
Purchase #5	$110.39	11.426%	$123.0032	$123.00	$123.00	$123.00
Purchase #6	$52.77	9.796%	$57.9393	$57.94	$57.95	$57.90
Purchase #7	$165.77	4.683%	$173.533	$173.53	$173.55	$173.50
7 purchase totals =	$848.61		$925.6569	$925.65	$925.70	$925.50