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	$110.79	3.493%	$114.6599	$114.66	$114.65	$114.70
Purchase #2	$181.47	4.352%	$189.3676	$189.37	$189.35	$189.40
Purchase #3	$73.92	13.470%	$83.877	$83.88	$83.90	$83.90
Purchase #4	$72.74	10.852%	$80.6337	$80.63	$80.65	$80.60
Purchase #5	$69.45	4.322%	$72.4516	$72.45	$72.45	$72.50
Purchase #6	$128.64	4.519%	$134.4532	$134.45	$134.45	$134.50
Purchase #7	$230.77	6.236%	$245.1608	$245.16	$245.15	$245.20
7 purchase totals =	$867.78		$920.6038	$920.60	$920.60	$920.80