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	$89.33	3.709%	$92.6432	$92.64	$92.65	$92.60
Purchase #2	$19.50	3.728%	$20.227	$20.23	$20.25	$20.20
Purchase #3	$236.98	3.543%	$245.3762	$245.38	$245.40	$245.40
Purchase #4	$158.41	9.172%	$172.9394	$172.94	$172.95	$172.90
Purchase #5	$109.51	9.387%	$119.7897	$119.79	$119.80	$119.80
Purchase #6	$91.36	7.778%	$98.466	$98.47	$98.45	$98.50
Purchase #7	$173.42	4.723%	$181.6106	$181.61	$181.60	$181.60
7 purchase totals =	$878.51		$931.0521	$931.06	$931.10	$931.00