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	$234.85	4.737%	$245.9748	$245.97	$245.95	$246.00
Purchase #2	$158.89	10.408%	$175.4273	$175.43	$175.45	$175.40
Purchase #3	$39.66	7.523%	$42.6436	$42.64	$42.65	$42.60
Purchase #4	$115.95	6.257%	$123.205	$123.21	$123.20	$123.20
Purchase #5	$97.86	6.681%	$104.398	$104.40	$104.40	$104.40
Purchase #6	$191.93	10.712%	$212.4895	$212.49	$212.50	$212.50
Purchase #7	$92.67	9.172%	$101.1697	$101.17	$101.15	$101.20
7 purchase totals =	$931.81		$1,005.3079	$1,005.31	$1,005.30	$1,005.30